Skip to main content
NCBI home page
ACS AuthorChoice logoLink to ACS AuthorChoice
. 2024 Mar 1;15(10):2658–2664. doi: 10.1021/acs.jpclett.4c00343

Conformer-Specific Photoelectron Spectroscopy of Carbonic Acid: H2CO3

Keisuke Kanayama †,‡,§, Hisashi Nakamura ‡, Kaoru Maruta ‡, Andras Bodi †, Patrick Hemberger †,*
PMCID: PMC10945571  PMID: 38426443

Abstract

graphic file with name jz4c00343_0006.jpg

Carbonic acid (H2CO3) is a fundamental species in biological, ecological, and astronomical systems. However, its spectroscopic characterization is incomplete because of its reactive nature. The photoionization (PI) and the photoion mass-selected threshold photoelectron (ms-TPE) spectra of H2CO3 were obtained by utilizing vacuum ultraviolet (VUV) synchrotron radiation and double imaging photoelectron photoion coincidence spectroscopy. Two carbonic acid conformers, namely, cis–cis and cis–trans, were identified. Experimental adiabatic ionization energies (AIEs) of cis–cis and cis–trans H2CO3 were determined to be 11.27 ± 0.02 and 11.18 ± 0.03 eV, and the cation enthalpies of formation could be derived as ΔfH°0K = 485 ± 2 and 482 ± 3 kJ mol–1, respectively. The cis–cis conformer shows intense peaks in the ms-TPES that are assigned to the C=O/C–OH stretching mode, while the cis–trans conformer exhibits a long progression to which two C=O/C–OH stretching modes contribute. The TPE spectra allow for the sensitive and conformer-selective detection of carbonic acid in terrestrial experiments to better understand astrochemical reactions.

Carbonic acid (H2CO3, 1) plays a fundamental role in our daily lives as constituent of the carbonate buffer stabilizing the pH of blood1 and as a contributor to ocean acidification.2,3 Laboratory experiments have been carried out on the production and spectroscopic characterization of 1 in the condensed phase to investigate its astrochemical role in water-rich ices when abundant CO2 and CO are present.4−13 Gaseous carbonic acid, 1, a long predicted component in extraterrestrial environments,14−16 has only recently been detected toward the Galactic Center molecular cloud G+0.693-0.027 by Yebes and IRAM radio telescope measurements.17 The chemistry of carbonic acid formation in the interstellar medium (ISM) is suggested to proceed at low temperatures along radical-driven routes on icy dust-grain surfaces yielding cis and trans HOCO radicals as intermediates, which form 1 upon reaction with a second hydroxyl radical.9 An electron-driven route followed by radical association reactions to form 1 was also suggested.16 These pathways may well be active in comets, such as Hale–Bopp, on the icy surfaces of the Galilean moons Europa and Callisto, as well as on Mars.18,19 Based on computational and IR spectroscopic studies,20−231 appears in three conformers with a relative stability of cis–cis (1cc) > cis–trans (1ct) ≫ trans–trans (1tt), as determined by intramolecular H-bonding and shown in Scheme 1. The formation of 1cc is further promoted by H atom tunneling in 1ct, as shown by Wagner et al.,24 which makes 1cc likely the most abundant conformer in the ISM. Indeed, Sanz-Novo et al. estimated the 1cc to 1ct ratio to be 25:1; however, they could only detect 1ct by radio astronomy because of the low dipole moment of 1cc.17

Scheme 1. Three Conformers of Carbonic Acid (1).

Scheme 1

Open in a new tab

Relative energies taken from Reisenauer et al.23

The spectroscopic characterization of gas-phase 1 is incomplete and limited to the infrared (IR) and microwave ranges. 1 was first captured by Terlouw et al.25 by heating ammonium bicarbonate (NH4HCO3) and using electron ionization mass spectrometry for detection. Mori et al.22,26 produced 1 using a pulsed discharge nozzle with a CO2/Ar/H2O and measured the microwave spectrum of both 1cc and 1ct. Bernard et al.27,28 investigated the IR spectra of 1 in a low temperature Ar matrix produced through protonation of HCO3– with HCl in a methanolic solution or with HBr in an aqueous solution.5,29 In a series of experiments the α- and β-polymorphs of solid 1 were discussed.5,18,27 This assignment was later corrected by the matrix isolation IR spectrum of Reisenauer et al.,23 who produced 1 via 2-fold isobutene (C4H8) loss from di-tert-butyl carbonate (DTBC, 2) by vacuum flash pyrolysis.30 They found that the methyl ester of carbonic acid caused the feature in the IR spectrum, incorrectly assigned to the α-polymorph.30

Multiplexed photoionization31,32 and photoelectron spectroscopic33−36 methods offer high sensitivity (<1 ppb),37 multiplicity (detection of various species at the same time), and high selectivity because constitutional isomers and diastereomers including conformers often have different ionization energies (AIEs) and vibronic structures. Thus, photoionization tools are ideally suited as a detection tool in terrestrial astrochemistry experiments to sample from complex reactive environments and probe the entire chemistry at conditions relevant to the interstellar medium. Photoelectron photoion coincidence (PEPICO) spectroscopy38−40 combines mass spectrometry and photoelectron spectroscopy to record photoion mass-selected threshold photoelectron spectra (ms-TPES). This allows for an isomer-selective assignment38 of reactive intermediates in catalysis,39 combustion,41 and in reactions modeling the ISM, which is a clear advantage compared to conventional photoelectron spectroscopy done in laboratories, suffering from spectral congestion due to the overlap of PE bands from different molecules.33 This motivated us to investigate 1 using vacuum ultraviolet (VUV) synchrotron radiation to obtain the threshold photoelectron spectrum, to determine cation energetics and the geometry change upon ionization as driven by the electronic structure of 1, similar to the approach employed for the picolyl radicals and m-xylylene or m-benzyne diradicals.42−44 This study will enable laboratory detection of 1 in complex reaction mixtures by means of photoionization and photoelectron spectroscopy, which is more sensitive as compared to conventional absorption methods (e.g., rotational spectroscopy).45 Furthermore, the ionization energies and the threshold photoelectron spectrum measured in this work are important properties to develop strategies to explore the excited states by resonance-enhanced multiphoton ionization (REMPI) and time-resolved photoelectron spectroscopy.

Carbonic acid (1) was produced by flash pyrolysis of the DTBC (2) precursor diluted in helium or argon following Reisenauer’s strategy.23 See the Supporting Information (SI) for other strategies25,46,47 to produce 1, which were also attempted but failed in this study. The pyrolysis products expanded into high vacuum and formed a molecular beam. The sample was ionized by VUV synchrotron radiation and detected by PEPICO spectroscopy. Mass spectra at 11.5 eV (Figure 1) show that the parent ion of the precursor (m/z 174) is not stable and extensive dissociative ionization occurs at room temperature, giving rise to peaks at m/z 57, 59, 112, 115, and 119. At ca. 760 K a small peak is seen at m/z 62, which is assigned to carbonic acid 1. Isobutene (C4H6, m/z 56) is formed as a byproduct of the reaction in Scheme 2. Lower mass products, such as m/z 28 and 41, are likely produced via parallel decomposition channels of 2 or dissociative photoionization of, for example, isobutene.48 Increasing the pyrolysis temperature to above 900 K increases the conversion of precursor 2 but leads to full depletion of 1 producing mainly water and CO2, emphasizing its reactive character. Further mass spectra of 1 at different conditions along with ion velocity map imaging (VMI) of m/z 62 (Figure S1) are detailed in the Supporting Information (SI) providing further evidence that 1 is indeed formed via pyrolysis of 2.

Figure 1.

Figure 1

Open in a new tab

Mass spectra at 11.5 eV during the production of gaseous carbonic acid (H2CO3, 1) from DTBC, 2. Extensive fragmentation at 300 K is responsible for the formation of m/z 119, 115, 112, 59, and 57. 1 (m/z 62) and isobutene (m/z 56) are produced in parallel according to Scheme 2, while 1 rapidly decomposes above 760 K.

Scheme 2. Decomposition of Carbonic Acid 1 via a Twofold Isobutene Loss from 2(23).

Scheme 2

Open in a new tab

The ms-TPES as well as photoionization (PI) spectra of carbonic acid 1, formed at a reactor temperature of 790 K, are shown in Figure 2. Thanks to velocity map imaging (VMI) the 300 K room-temperature spectra can be obtained after rethermalization in the detection chamber, as detailed in the Supporting Information (Figure S2a,b). Moreover, the spectra do not have any contributions from neighboring masses, as shown in Figures S2c. The PI spectrum of m/z 62 starts to rise at around 11.18 eV and plateaus at 11.7 eV. On the one hand, the PI spectrum of carbonic acid is likely unique among m/z 62 species, but being broad and featureless, it lacks conformer-selectivity. The ms-TPES of m/z 62, on the other hand, clearly shows four intense peaks at 11.27, 11.45, 11.64, and 11.81 eV. Additional low-intensity bands are detected at 11.39, 11.50, 11.59, and 11.70 eV. We calculated adiabatic ionization energies (AIEs) of the three conformers, 1cc, 1ct, and 1tt, using composite and EOM-CCSD methods as shown in Table 1 and Table S1, and found them to be 11.29, 11.22, and 11.08 eV, respectively, at the W1BD level of theory, which usually delivers better than chemical accuracy (1 kcal mol–1, 43 meV, 4.2 kJ mol–1).49 According to the calculated potential energy surface of 1,22,231tt is 42 kJ mol–1 less stable than 1cc and 1ct with a low-energy transition state in between. In thermal equilibrium at a reactor temperature of 790 K, the relative abundance of 1cc:1ct:1tt is predicted to be 2.6:1:4.4 × 10–3 at the W1BD level of theory, meaning that 1tt is unlikely to contribute to the signal above the detection limit. Thus, based on the ms-TPE and PI spectra, the first intense peak at 11.27 eV in the former and the onset of the latter at 11.18 eV are assigned to the AIEs of 1cc and 1ct, respectively, with the help of Franck–Condon (FC) simulations (see below). These numbers are also in good agreement with the W1BD calculations, with a difference of 20 and 40 meV for 1cc and 1ct, respectively.

Figure 2.

Figure 2

Open in a new tab

Photoion mass-selected threshold photoelectron (ms-TPE) and photoionization (PI) spectra of carbonic acid 1 (black and gray). Colored lines and sticks are Franck–Condon simulations for the transition from neutral to cation ground states of 1cc (red) and 1ct (blue) calculated at 300 K and at the B3LYP/6-311++G(d,p) level of theory. The stick spectra are convolved with a Gaussian function with a full width at half-maximum of 33 meV to account for the rotational envelope. The sum of the 1cc and 1ct simulations is colored magenta and represents the features in the experimental spectrum well.

Table 1. Experimental and Calculated Adiabatic Ionization Energies (AIEs) of the Three Conformers of Carbonic Acid 1.

AIE (eV) 1cc 1ct 1tt
Experiment 11.27 ± 0.02 11.18 ± 0.03a  
G4 11.23 11.16 11.02
CBS-APNO 11.27 11.21 11.08
W1BD 11.29 11.22 11.08
EOM-IP-CCSD/cc-pVQZ 11.22 11.16  
Open in a new tab
a

Determined based on the FC simulation fitted to the ms-TPES.

To assign the conformers of 1 and to obtain spectroscopic insights, Franck–Condon (FC) simulations were fitted to the bands of the ms-TPES (Figure 2). The simulation of 1cc (red lines, Figure 2, Figure S3b) is in good agreement with the intense peaks at 11.27, 11.45, 11.64, and 11.81 eV. Thus, the first clear peak at 11.27 ± 0.02 eV is assigned to the AIE of 1cc, i.e., the transition into the cations’ (1cc+) vibrational ground state, also in excellent agreement with the composite method results (Table 1). The following intense peaks (11.45, 11.64, and 11.81 eV) are assigned to a C=O/C–OH stretching mode of 1cc+ (ν+2) with a progression of ca. 183 ± 20 meV (1478 ± 160 cm–1, see Figure 2), which compares well with the calculated value of 1503 cm–1 at the B3LYP/6-311++G(d,p) level of theory (Table S2 in SI). Exciting an HO–C–OH bending mode, ν+5, and combination bands of ν+5 and (ν+2) give rise to the low-intensity bands in the ms-TPES at 11.34, 11.52, and 11.71 eV, respectively.

However, the FC spectrum of 1cc does not explain the bands at 11.39 and between 11.55 and 11.65 eV, as shown in Figure S3a,b in the Supporting Information. This could be remedied by adding the FC simulation of 1ct (blue lines, Figure 2), which, unlike the FC simulation of 1cc, shows a long progression with only a few well-resolved peaks. We relied on the most intense of the remaining bands at 11.39 eV and between 11.55 and 11.65 eV to reproduce the missing bands in the ms-TPES using the 1ct FC simulation (Figure 2 and Figure S3c). This resulted in a good match to all observed features of the experimental spectrum (magenta lines in Figure 2). Generally, FC factors for 1ct are only one-third of those for 1cc, which makes a quantitative analysis of the relative abundances challenging. Furthermore, autoionization may contribute to the threshold ionization signal of the conformers differently, and the photoelectron dipole matrix elements may also be different for the conformers; therefore, a discussion of the relative ratio of 1cc and 1ct may be misleading. Alternative fits, where the 0–0 transition of 1ct was set to 11.21 and 11.24 eV, respectively, are discussed in the SI (Figure S4a,b) and were disregarded. Based on the fitted 1ct FC spectrum and the rising edge of the PI spectrum, the experimental AIE of 1ct is determined to be 11.18 ± 0.03 eV, with a slightly larger uncertainty than for 1cc. This is found to be well within single and averaged composite method calculations (see Table 1 and Table S1), with expected chemical accuracy (1 kcal mol–1/4.2 kcal mol–1/43 meV).49 Major vibrational modes of 1ct+ are an HO–C–OH bending mode (ν+8) and two C=O/C–OH stretching vibrations (ν+4 and ν+3), shown in Figure 2. To test the sturdiness of the assignment, we also conducted FC simulations using different levels of theory and found that they were generally consistent with the B3LYP results, which agreed best with the experimental ms-TPES (Figure S5). Thanks to the good overlap of the simulation and the experimental spectra, two conformers of carbonic acid 1, 1cc and 1ct, can be identified as the spectral carriers of the ms-TPES. Beyond the sensitive detection of 1 in reactive mixtures, the spectra also allow for the assignment of two conformers out of the three possible. The much lower computed ionization energy of the high-energy 1tt conformer implies that its photoionization signal could likely be assigned selectively too, if abundant enough. Thus, the combination of photoelectron and photoionization spectroscopy is a well-suited tool for the conformer-selective identification of carbonic acid in photoionization-based experiments to unveil the chemistry of the ISM in terrestrial experiments. As the heat of formation of neutral 1 is listed in the Active Thermochemical Tables (ATcT),50 the experimental ionization energies can be simply added to derive the enthalpies of formation of the cation conformers as ΔfH°0K = 485 ± 2 and 482 ± 3 kJ mol–1 for 1cc+ and 1ct+, respectively. These thermochemical parameters can be utilized to calculate reaction enthalpies in ion–molecule reactions leading to or from 1+ in astrochemical models.51,52

Besides acting as a fingerprint for the detection of 1 in reactive mixtures, the ms-TPES provides insights into the geometry change upon ionization and, thus, into the electronic structure of 1cc and 1ct. The highest occupied molecular orbitals (HOMOs) of 1cc and 1ct are shown in Figure 3. Both show nonbonding character at the oxygen atoms. The bare oxygen atom (O2) possesses the largest contribution, while the other two oxygen atoms (O1 and O3) have only smaller ones. Upon ionization of 1cc, the O1–C–O3 and two H–O–C angles increase (Table S3 in the SI) due to less repulsion from the lone pairs by reducing the electron density on the oxygen atom. Consequently, the C=O bond length elongates, while two C–OH bonds shorten, resulting in three almost equal C–O bond distances upon ionization (Table S3). It is intriguing to mention that the intramolecular O···HO distance also increases upon ionization in 1cc (2.32 to 2.39 Å) and 1ct (2.17 to 2.37 Å), respectively. This may be explained by the increased positive polarization at the oxygen atoms upon ionization, which may lower their hydrogen bond acceptor capability in the cation. Spectroscopically, this change in geometry is mirrored by two totally symmetric vibrational modes of 1cc+ observed in the ms-TPES, the HO–C–OH bending (ν+5, a1) and the C=O/C–OH stretching (ν+2, a1) vibration. A similar geometry change occurs also in 1ct, but due to its lower symmetry (Cs vs C2v), two vibrational modes are active, differing in the cis and trans C–OH stretch contributions (ν+4 = 1492 cm–1 and ν+3= 1685 cm–1 both a′). The equivalent mode (ν+10) in 1cc is not active, due to its b2 symmetry. This intensity sharing in 1ct leads to smaller FC factors as compared to those in 1cc. However, the photoelectron spectra of 1cc and 1ct, in which the peaks for 1ct are less intense than those of 1cc, were successfully obtained using PEPICO spectroscopy. It is also worth mentioning that 1ct+ and 1cc+ are quasi-isoenergetic at the W1BD level of theory or by utilizing the experimentally determined AIEs together with the ΔfH°0K of the neutral. This may suggest a close-to-equal 1ct+ and 1cc+ abundance in equilibrium when the cation is formed in the interstellar medium.

Figure 3.

Figure 3

Open in a new tab

Highest occupied molecular orbitals (HOMO) of the two conformers of carbonic acid 1, (left) 1cc, and (right) 1ct. The numbering of each atom in the discussion is also presented.

In conclusion, carbonic acid (H2CO3, 1) was produced by flash pyrolysis of di-tert-butyl carbonate (2)23 and detected utilizing photoelectron photoion coincidence (PEPICO) spectroscopy with vacuum ultraviolet (VUV) synchrotron radiation. Based on the recorded PI spectrum and ms-TPES and Franck–Condon simulations, the two most stable conformers of 1, cis–cis (1cc) and cis–trans (1ct), could be identified. Together with the adiabatic ionization energies (AIEs), these conformer-specific spectroscopic fingerprints are accessible in the PhotoElectron PhotoIon Spectral COmpendium (PEPISCO) database.53 Our spectroscopic data lay the foundation for employing photoionization and photoelectron spectroscopic methods to identify and ideally quantify 1cc and 1ct in terrestrial photoionization experiments to study astrochemically relevant reactions at VUV synchrotron facilities around the globe31,40,41,54 to probe the gas-phase formation of 1, via, for example, radical recombination reactions (HOCO + OH) similar to surface pathways.9 In addition, our measured PI and TPE spectra and the determined AIEs may help to enable time-resolved pump–probe photoionization experiments from nano- down to femtoseconds to measure the lifetime and the fate of excited 1, which may contribute to improve astrochemical models. Furthermore, our ms-TPES and computational analyses provide thermochemical parameters, such as ionization energies and heats of formation, as well as insights into the electronic structure of 1, especially regarding molecular orbitals and geometries of both the neutral and cation.

Experimental Section

The experiment was conducted utilizing the double imaging photoelectron photoion coincidence (i2PEPICO) endstation at the vacuum ultraviolet (VUV) beamline of the Swiss Light Source (SLS) located at Paul Scherrer Institute, Switzerland.54−57 Di-tert-butyl carbonate purchased from abcr GmbH (95% purity) was used as a precursor to produce carbonic acid (H2CO3, 1) through flash vacuum pyrolysis. The precursor was placed in a container at a pressure of ca. 150 mbar at room temperature between a mass flow controller (MKS Instruments Inc.) and a high-vacuum molecular beam (MB) source chamber (10–5 mbar). The vaporized precursor was introduced into a resistively heated Chen-type SiC microtubular reactor58 (ca. 40 mm length, 1 mm inner diameter, 2 mm outer diameter, and 15 mm heated length) installed in the MB source chamber at a flow rate of 20 sccm argon (≥99.998%, PanGas) or helium (≥99.996%, PanGas). The correlation between the reactor temperature and output wattage had been calibrated before. The gas temperature close to the reactor centerline is predicted to be approximately 10% lower than the reactor surface temperature.59,60 Pressure and residence time in the reactor are estimated to be around 10–20 mbar and 10–50 μs, respectively.58−60 The pyrolyzed gases leaving the reactor expand into a high vacuum (10–5 mbar), forming a MB. The MB is skimmed using a Model 2 nickel skimmer (Beam Dynamics Inc., 2 mm aperture) and enters the ionization chamber (10–7 mbar) of the PEPICO spectrometer, where it is photoionized by VUV synchrotron radiation. VUV light is provided by a bending magnet, collimated onto a plane blazed grating (150 grooves mm–1) with a resolving power of 1500, and focused on the exit slit (200 μm). A differentially pumped rare gas filter between the focusing mirror and the endstation, filled with a neon/argon mixture at 8.5 mbar over 10 cm suppresses higher-order radiation from the grating.55 Photoions and photoelectrons are accelerated in opposite directions under a constant electric field of 218 V cm–1 and detected by position-sensitive delay line anode detectors (DLD40, Roentdek) in delayed coincidence.61 This enables time-of-flight (TOF) detection for cations and velocity map imaging (VMI) of both cations and electrons. Photoion mass-selected photoelectron spectrum (ms-TPES) as well as photoionization (PI) spectrum were recorded by scanning the photon energy in 10 meV steps from 11.10 to 11.87 eV with an integration time of 350 s per point. As for the ms-TPES, electrons with less than 10 meV kinetic energy were selected based on the photoelectron VMI. The threshold electrons in coincidence with cations in the room-temperature background signals arriving in the TOF range of interest were extracted based on the ion VMI to suppress hot band contributions.62 Contributions of hot electrons that possess higher kinetic energy without off-axis momentum components were also subtracted.63

Gaussian 1664 and Q-Chem 4.365 were used for the computations. Geometry optimization and vibrational frequency calculations of the ground states were performed at the B3LYP/6-311++G(d,p), ωB97X-D/6-311++G(d,p), M06/6-311++G(d,p), G3, G4, CBS-QB3, CBS-APNO, W1BD, MP2/6-311++G(d,p), and CCSD/cc-pVTZ levels of theory. We used the Mulliken notation for the numbering of unscaled vibrational modes. Cation excited-state calculations were performed at the TD-B3LYP/6-311++G(d,p) level of theory but will contribute to the ms-TPES only above the investigated energy range. Adiabatic ionization energies were calculated with the aforementioned methods as well as at the (EOM-IP-)CCSD/cc-pVQZ level of theory, while the geometry optimization and vibrational frequencies were calculated utilizing (EOM-IP-)CCSD/cc-pVDZ. Franck–Condon (FC) simulations were performed at 300 K with the Franck–Condon–Herzberg–Teller method implemented in Gaussian 16,64 and the stick spectra were convolved with a Gaussian function with a full width at half-maximum of 33 meV.

Acknowledgments

The experimental work has been carried out at the VUV beamline of the Swiss Light Source, located at Paul Scherrer Institute, Villigen, Switzerland. K.K. acknowledges the support from JSPS KAKENHI Grant Number 22J13787 and IFS-GCORE Overseas Dispatch Program. The authors thank Patrick Ascher for technical assistance and Mathias Steglich for performing some initial experiments on carbonic acid 1.

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.jpclett.4c00343.

  • Figure S1: Additional mass spectra and velocity map images; Figures S2, S3 and S4, S5: obtained room temperature ms-TPES (m/z 59, 60, 62) and additional Franck–Condon fits; Tables S1–S3: Calculated ionization energies, optimized geometries, and vibrational frequencies (PDF)

The authors declare no competing financial interest.

Supplementary Material

jz4c00343_si_001.pdf (788.3KB, pdf)

References

  1. Adamczyk K.; Prémont-Schwarz M.; Pines D.; Pines E.; Nibbering E. T. J. Real-Time Observation of Carbonic Acid Formation in Aqueous Solution. Science 2009, 326, 1690–1694. 10.1126/science.1180060. [DOI] [PubMed] [Google Scholar]
  2. Caldeira K.; Wickett M. E. Anthropogenic carbon and ocean pH. Nature 2003, 425 (6956), 365–365. 10.1038/425365a. [DOI] [PubMed] [Google Scholar]
  3. Reddy S. K.; Balasubramanian S. Carbonic acid: Molecule, crystal and aqueous solution. Chem. Com. 2014, 50 (5), 503–514. 10.1039/C3CC45174G. [DOI] [PubMed] [Google Scholar]
  4. Moore M. H.; Khanna R. K. Infrared and mass spectral studies of proton irradiated H2O + CO2 ice: Evidence for carbonic acid. Spectrochim. Acta, Part A 1991, 47 (2), 255–262. 10.1016/0584-8539(91)80097-3. [DOI] [Google Scholar]
  5. Hage W.; Hallbrucker A.; Mayer E. Metastable intermediates from glassy solutions part 5: FTIR spectroscopic characterization of isolated α- and β-carbonic acid. J. Mol. Struct. 1997, 408–409, 527–531. 10.1016/S0022-2860(96)09701-3. [DOI] [Google Scholar]
  6. Brucato J.; Palumbo M.; Strazzulla G. Carbonic Acid by Ion Implantation in Water/Carbon Dioxide Ice Mixtures. Icarus 1997, 125 (1), 135–144. 10.1006/icar.1996.5561. [DOI] [Google Scholar]
  7. Gerakines P. A.; Moore M. H.; Hudson R. L. Carbonic acid production in H2O:CO2 ices - UV photolysis vs. proton bombardment. Astron. Astrophys. 2000, 357 (2), 793–800. [Google Scholar]
  8. Garozzo M.; Fulvio D.; Gomis O.; Palumbo M. E.; Strazzulla G. H-implantation in SO2 and CO2 ices. Planet. Space Sci. 2008, 56 (9), 1300–1308. 10.1016/j.pss.2008.05.002. [DOI] [Google Scholar]
  9. Oba Y.; Watanabe N.; Kouchi A.; Hama T.; Pirronello V. Formation of Carbonic Acid (H2CO3) by Surface Reactions of Non-energetic OH Radicals with CO Molecules at Low Temperatures. Astrophys. J. 2010, 722 (2), 1598–1606. 10.1088/0004-637X/722/2/1598. [DOI] [Google Scholar]
  10. Jones B. M.; Kaiser R. I.; Strazzulla G. UV-VIS, infrared, and mass spectroscopy of electron irradiated frozen oxygen and carbon dioxide mixtures with water. Astrophys. J. 2014, 781 (2), 85. 10.1088/0004-637X/781/2/85. [DOI] [Google Scholar]
  11. Pavithraa S.; Lo J. I.; Cheng B. M.; Sekhar B. N. R.; Mason N. J.; Sivaraman B. Identification of a unique VUV photoabsorption band of carbonic acid for its identification in radiation and thermally processed water-carbon dioxide ices. Spectrochim. Acta, Part A 2019, 215, 130–132. 10.1016/j.saa.2019.02.037. [DOI] [PubMed] [Google Scholar]
  12. Wang X.; Bürgi T. Observation of Carbonic Acid Formation from Interaction between Carbon Dioxide and Ice by Using In Situ Modulation Excitation IR Spectroscopy. Angew. Chem., Int. Ed. 2021, 60 (14), 7860–7865. 10.1002/anie.202015520. [DOI] [PubMed] [Google Scholar]
  13. Ioppolo S.; Kaňuchová Z.; James R. L.; Dawes A.; Ryabov A.; Dezalay J.; Jones N. C.; Hoffmann S. V.; Mason N. J.; Strazzulla G. Vacuum ultraviolet photoabsorption spectroscopy of space-related ices: Formation and destruction of solid carbonic acid upon 1 keV electron irradiation. Astron. Astrophys. 2021, 646, A172. 10.1051/0004-6361/202039184. [DOI] [Google Scholar]
  14. Strazzulla G.; Brucato J. R.; Cimino G.; Palumbo M. E. Carbonic acid on Mars?. Planet. Space Sci. 1996, 44 (11), 1447–1450. 10.1016/S0032-0633(96)00079-7. [DOI] [Google Scholar]
  15. Delitsky M. L.; Lane A. L. Ice chemistry on the Galilean satellites. J. Geophys. Res. 1998, 103 (E13), 31391–31403. 10.1029/1998JE900020. [DOI] [Google Scholar]
  16. Zheng W.; Kaiser R. I. On the formation of carbonic acid (H2CO3) in solar system ices. Chem. Phys. Lett. 2007, 450 (1–3), 55–60. 10.1016/j.cplett.2007.10.094. [DOI] [Google Scholar]
  17. Sanz-Novo M.; Rivilla V. M.; Jiménez-Serra I.; Martín-Pintado J.; Colzi L.; Zeng S.; Megías A.; López-Gallifa Á.; Martínez-Henares A.; Massalkhi S.; et al. Discovery of the Elusive Carbonic Acid (HOCOOH) in Space. Astrophys. J. 2023, 954, 3. 10.3847/1538-4357/ace523. [DOI] [Google Scholar]
  18. Hage W.; Liedl K. R.; Hallbrucker A.; Mayer E. Carbonic acid in the gas phase and its astrophysical relevance. Science 1998, 279 (5355), 1332–1335. 10.1126/science.279.5355.1332. [DOI] [PubMed] [Google Scholar]
  19. Peeters Z.; Hudson R. L.; Moore M. H.; Lewis A. The formation and stability of carbonic acid on outer Solar System bodies. Icarus 2010, 210 (1), 480–487. 10.1016/j.icarus.2010.06.002. [DOI] [Google Scholar]
  20. Nguyen M. T.; Ha T. K. A Theoretical Study of the Formation of Carbonic Acid from the Hydration of Carbon Dioxide: A Case of Active Solvent Catalysis. J. Am. Chem. Soc. 1984, 106 (3), 599–602. 10.1021/ja00315a023. [DOI] [Google Scholar]
  21. Wight C. A.; Boldyrev A. I. Potential energy surface and vibrational frequencies of carbonic acid. J. Phys. Chem. 1995, 99 (32), 12125–12130. 10.1021/j100032a012. [DOI] [Google Scholar]
  22. Mori T.; Suma K.; Sumiyoshi Y.; Endo Y. Spectroscopic detection of isolated carbonic acid. J. Chem. Phys. 2009, 130 (20), 204308–204308. 10.1063/1.3141405. [DOI] [PubMed] [Google Scholar]
  23. Reisenauer H. P.; Wagner J. P.; Schreiner P. R. Gas-Phase Preparation of Carbonic Acid and Its Monomethyl Ester. Angew. Chem., Int. Ed. 2014, 53 (44), 11766–11771. 10.1002/anie.201406969. [DOI] [PubMed] [Google Scholar]
  24. Wagner J. P.; Reisenauer H. P.; Hirvonen V.; Wu C.-H.; Tyberg J. L.; Allen W. D.; Schreiner P. R. Tunnelling in carbonic acid. Chem. Com. 2016, 52 (50), 7858–7861. 10.1039/C6CC01756H. [DOI] [PubMed] [Google Scholar]
  25. Terlouw J. K.; Lebrilla C. B.; Schwarz H. Thermolysis of NH4HCO3—A Simple Route to the Formation of Free Carbonic Acid(H2CO3) in the Gas Phase. Angew. Chem., Int. Ed. 1987, 26 (4), 354–355. 10.1002/anie.198703541. [DOI] [Google Scholar]
  26. Mori T.; Suma K.; Sumiyoshi Y.; Endo Y. Spectroscopic detection of the most stable carbonic acid, cis-cis H2CO3. J. Chem. Phys. 2011, 134 (4), 044319–044319. 10.1063/1.3532084. [DOI] [PubMed] [Google Scholar]
  27. Bernard J.; Huber R. G.; Liedl K. R.; Grothe H.; Loerting T. Matrix Isolation Studies of Carbonic Acid—The Vapor Phase above the β-Polymorph. J. Am. Chem. Soc. 2013, 135 (20), 7732–7737. 10.1021/ja4020925. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Bernard J.; Seidl M.; Kohl I.; Liedl K. R.; Mayer E.; Gálvez Ó.; Grothe H.; Loerting T. Spectroscopic Observation of Matrix-Isolated Carbonic Acid Trapped from the Gas Phase. Angew. Chem., Int. Ed. 2011, 50 (8), 1939–1943. 10.1002/anie.201004729. [DOI] [PubMed] [Google Scholar]
  29. Hage W.; Hallbrucker A.; Mayer E. Carbonic acid: synthesis by protonation of bicarbonate and FTIR spectroscopic characterization via a new cryogenic technique. J. Am. Chem. Soc. 1993, 115 (18), 8427–8431. 10.1021/ja00071a061. [DOI] [Google Scholar]
  30. Bucher G.; Sander W. Clarifying the structure of carbonic acid. Science 2014, 346 (6209), 544–545. 10.1126/science.1260117. [DOI] [PubMed] [Google Scholar]
  31. Parker D. S. N.; Kaiser R. I.; Troy T. P.; Ahmed M. Hydrogen Abstraction/Acetylene Addition Revealed. Angew. Chem., Int. Ed. 2014, 53 (30), 7740–7744. 10.1002/anie.201404537. [DOI] [PubMed] [Google Scholar]
  32. Yang T.; Kaiser R. I.; Troy T. P.; Xu B.; Kostko O.; Ahmed M.; Mebel A. M.; Zagidullin M. V.; Azyazov V. N. HACA’s Heritage: A Free-Radical Pathway to Phenanthrene in Circumstellar Envelopes of Asymptotic Giant Branch Stars. Angew. Chem., Int. Ed. 2017, 56 (16), 4515–4519. 10.1002/anie.201701259. [DOI] [PubMed] [Google Scholar]
  33. Bouwman J.; McCabe M. N.; Shingledecker C. N.; Wandishin J.; Jarvis V.; Reusch E.; Hemberger P.; Bodi A. Five-membered ring compounds from the ortho-benzyne + methyl radical reaction under interstellar conditions. Nat. Astron. 2023, 7 (4), 423–430. 10.1038/s41550-023-01893-2. [DOI] [Google Scholar]
  34. McCabe M. N.; Hemberger P.; Reusch E.; Bodi A.; Bouwman J. Off the Beaten Path: Almost Clean Formation of Indene from the ortho-Benzyne + Allyl Reaction. J. Phys. Chem. Lett. 2020, 11 (8), 2859–2863. 10.1021/acs.jpclett.0c00374. [DOI] [PMC free article] [PubMed] [Google Scholar]
  35. Tuli L. B.; Goettl S. J.; Turner A. M.; Howlader A. H.; Hemberger P.; Wnuk S. F.; Guo T.; Mebel A. M.; Kaiser R. I. Gas phase synthesis of the C40 nano bowl C40H10. Nat. Commun. 2023, 14 (1), 1527–1527. 10.1038/s41467-023-37058-y. [DOI] [PMC free article] [PubMed] [Google Scholar]
  36. Goettl S. J.; Tuli L. B.; Turner A. M.; Reyes Y.; Howlader A. H.; Wnuk S. F.; Hemberger P.; Mebel A. M.; Kaiser R. I. Gas-Phase Synthesis of Coronene through Stepwise Directed Ring Annulation. J. Am. Chem. Soc. 2023, 145, 15443–15455. 10.1021/jacs.3c03816. [DOI] [PubMed] [Google Scholar]
  37. Wen Z.; Tang X.; Fittschen C.; Zhang C.; Wang T.; Wang C.; Gu X.; Zhang W. Online analysis of gas-phase radical reactions using vacuum ultraviolet lamp photoionization and time-of-flight mass spectrometry. Rev. Sci. Instrum. 2020, 91 (4), 043201. 10.1063/1.5135387. [DOI] [PubMed] [Google Scholar]
  38. Hemberger P.; Bodi A.; Bierkandt T.; Köhler M.; Kaczmarek D.; Kasper T. Photoelectron Photoion Coincidence Spectroscopy Provides Mechanistic Insights in Fuel Synthesis and Conversion. Energy Fuels 2021, 35, 16265–16302. 10.1021/acs.energyfuels.1c01712. [DOI] [Google Scholar]
  39. Hemberger P.; van Bokhoven J. A.; Pérez-Ramírez J.; Bodi A. New analytical tools for advanced mechanistic studies in catalysis: Photoionization and photoelectron photoion coincidence spectroscopy. Catal. Sci. Technol. 2020, 10 (7), 1975–1990. 10.1039/C9CY02587A. [DOI] [Google Scholar]
  40. Bodi A.; Hemberger P.; Osborn D. L.; Sztáray B. Mass-Resolved Isomer-Selective Chemical Analysis with Imaging Photoelectron Photoion Coincidence Spectroscopy. J. Phys. Chem. Lett. 2013, 4 (17), 2948–2952. 10.1021/jz401500c. [DOI] [Google Scholar]
  41. Krüger J.; Garcia G. A.; Felsmann D.; Moshammer K.; Lackner A.; Brockhinke A.; Nahon L.; Kohse-Höinghaus K. Photoelectron-photoion coincidence spectroscopy for multiplexed detection of intermediate species in a flame. Phys. Chem. Chem. Phys. 2014, 16 (41), 22791–22804. 10.1039/C4CP02857K. [DOI] [PubMed] [Google Scholar]
  42. Reusch E.; Holzmeier F.; Constantinidis P.; Hemberger P.; Fischer I. Isomer-Selective Generation and Spectroscopic Characterization of Picolyl Radicals. Angew. Chem., Int. Ed. 2017, 56 (27), 8000–8003. 10.1002/anie.201703433. [DOI] [PubMed] [Google Scholar]
  43. Steglich M.; Custodis V. B. F.; Trevitt A. J.; DaSilva G.; Bodi A.; Hemberger P. Photoelectron Spectrum and Energetics of the meta-Xylylene Diradical. J. Am. Chem. Soc. 2017, 139, 14348–14351. 10.1021/jacs.7b06714. [DOI] [PubMed] [Google Scholar]
  44. Gerlach M.; Karaev E.; Schaffner D.; Hemberger P.; Fischer I. Threshold Photoelectron Spectrum of m-Benzyne. J. Phys. Chem. Lett. 2022, 13 (48), 11295–11299. 10.1021/acs.jpclett.2c03216. [DOI] [PubMed] [Google Scholar]
  45. Harris B.A Chirped Pulse Fourier Transform Millimeter Wave Spectrometer for Room Temperature, Gas Mixture Analysis. Ph.D. Dissertation, University of Virginia, 2014. [Google Scholar]
  46. Bucher G. Ester Pyrolysis of Carbonates: Bis(benzene hydrate) Carbonate as Potential Precursor for Monomeric Carbonic Acid. Eur. J. Org. Chem. 2010, 2010 (6), 1070–1075. 10.1002/ejoc.200901212. [DOI] [Google Scholar]
  47. Sun W.; Huang C.; Tao T.; Zhang F.; Li W.; Hansen N.; Yang B. Exploring the high-temperature kinetics of diethyl carbonate (DEC) under pyrolysis and flame conditions. Combust. Flame 2017, 181, 71–81. 10.1016/j.combustflame.2017.03.009. [DOI] [Google Scholar]
  48. Wang J.; Yang B.; Cool T. A.; Hansen N.; Kasper T. Near-threshold absolute photoionization cross-sections of some reaction intermediates in combustion. Int. J. Mass Spectrom. 2008, 269 (3), 210–220. 10.1016/j.ijms.2007.10.013. [DOI] [Google Scholar]
  49. Simmie J. M.; Somers K. P. Benchmarking Compound Methods (CBS-QB3, CBS-APNO, G3, G4, W1BD) against the Active Thermochemical Tables: A Litmus Test for Cost-Effective Molecular Formation Enthalpies. J. Phys. Chem. A 2015, 119 (28), 7235–7246. 10.1021/jp511403a. [DOI] [PubMed] [Google Scholar]
  50. Ruscic B.Active Thermochemical Tables (ATcT) ver. 1.124. https://atct.anl.gov/ (accessed 08-25-2023).
  51. Thaddeus P.; Guelin M.; Linke R. A. Three new ’nonterrestrial’ molecules. Astrophys. J. 1981, 246, L41–L45. 10.1086/183549. [DOI] [Google Scholar]
  52. Majumdar L.; Gratier P.; Wakelam V.; Caux E.; Willacy K.; Ressler M. E. Detection of HOCO+ in the protostar IRAS 16293–2422. Mon. Not. R. Astron. Soc. 2018, 477 (1), 525–530. 10.1093/mnras/sty703. [DOI] [Google Scholar]
  53. Hemberger P.; Pan Z.; Wu X.; Zhang Z.; Kanayama K.; Bodi A. Photoion Mass-Selected Threshold Photoelectron Spectroscopy to Detect Reactive Intermediates in Catalysis: From Instrumentation and Examples to Peculiarities and a Database. J. Phys. Chem. C 2023, 127 (34), 16751–16763. 10.1021/acs.jpcc.3c03120. [DOI] [PMC free article] [PubMed] [Google Scholar]
  54. Sztáray B.; Voronova K.; Torma K. G.; Covert K. J.; Bodi A.; Hemberger P.; Gerber T.; Osborn D. L. CRF-PEPICO: Double velocity map imaging photoelectron photoion coincidence spectroscopy for reaction kinetics studies. J. Chem. Phys. 2017, 147, 013944. 10.1063/1.4984304. [DOI] [PubMed] [Google Scholar]
  55. Johnson M.; Bodi A.; Schulz L.; Gerber T. Vacuum ultraviolet beamline at the Swiss Light Source for chemical dynamics studies. Nucl. Instrum. Methods Phys. Res. A 2009, 610 (2), 597–603. 10.1016/j.nima.2009.08.069. [DOI] [Google Scholar]
  56. Bodi A.; Johnson M.; Gerber T.; Gengeliczki Z.; Sztáray B.; Baer T. Imaging photoelectron photoion coincidence spectroscopy with velocity focusing electron optics. Rev. Sci. Instrum. 2009, 80 (3), 034101. 10.1063/1.3082016. [DOI] [PubMed] [Google Scholar]
  57. Bodi A.; Hemberger P.; Gerber T.; Sztáray B. A new double imaging velocity focusing coincidence experiment: i2PEPICO. Rev. Sci. Instrum. 2012, 83, 083105. 10.1063/1.4742769. [DOI] [PubMed] [Google Scholar]
  58. Kohn D. W.; Clauberg H.; Chen P. Flash pyrolysis nozzle for generation of radicals in a supersonic jet expansion. Rev. Sci. Instrum. 1992, 63 (8), 4003–4005. 10.1063/1.1143254. [DOI] [Google Scholar]
  59. Guan Q.; Urness K. N.; Ormond T. K.; David D. E.; Barney Ellison G.; Daily J. W. The properties of a micro-reactor for the study of the unimolecular decomposition of large molecules. Int. Rev. Phys. Chem. 2014, 33 (4), 447–487. 10.1080/0144235X.2014.967951. [DOI] [Google Scholar]
  60. Grimm S.; Baik S.-J.; Hemberger P.; Bodi A.; Kempf A. M.; Kasper T.; Atakan B. Gas-phase aluminium acetylacetonate decomposition: revision of the current mechanism by VUV synchrotron radiation. Phys. Chem. Chem. Phys. 2021, 23 (28), 15059–15075. 10.1039/D1CP00720C. [DOI] [PubMed] [Google Scholar]
  61. Bodi A.; Sztáray B.; Baer T.; Johnson M.; Gerber T. Data acquisition schemes for continuous two-particle time-of-flight coincidence experiments. Rev. Sci. Instrum. 2007, 78 (8), 084102. 10.1063/1.2776012. [DOI] [PubMed] [Google Scholar]
  62. Hemberger P.; Wu X.; Pan Z.; Bodi A. Continuous Pyrolysis Microreactors: Hot Sources with Little Cooling? New Insights Utilizing Cation Velocity Map Imaging and Threshold Photoelectron Spectroscopy. J. Phys. Chem. A 2022, 126 (14), 2196–2210. 10.1021/acs.jpca.2c00766. [DOI] [PubMed] [Google Scholar]
  63. Sztáray B.; Baer T. Suppression of hot electrons in threshold photoelectron photoion coincidence spectroscopy using velocity focusing optics. Rev. Sci. Instrum. 2003, 74 (8), 3763–3768. 10.1063/1.1593788. [DOI] [PubMed] [Google Scholar]
  64. Frisch M. J.; Trucks G. W.; Schlegel H. B.; Scuseria G. E.; Robb M. A.; Cheeseman J. R.; Scalmani G.; Barone V.; Petersson G. A.; Nakatsuji H., et al. Gaussian 16, Rev. C.01; 2019. [Google Scholar]
  65. Shao Y.; Gan Z.; Epifanovsky E.; Gilbert A. T. B.; Wormit M.; Kussmann J.; Lange A. W.; Behn A.; Deng J.; Feng X.; et al. Advances in molecular quantum chemistry contained in the Q-Chem 4 program package. Mol. Phys. 2015, 113 (2), 184–215. 10.1080/00268976.2014.952696. [DOI] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

jz4c00343_si_001.pdf (788.3KB, pdf)

Articles from The Journal of Physical Chemistry Letters are provided here courtesy of American Chemical Society

RESOURCES