. 2018 Aug 3;115(33):8301–8306. doi: 10.1073/pnas.1804671115

Table 1.

Dimers identified in SOA produced from the O₃-initiated oxidation of β-pinene that exhibited a significant decrease in abundance (>65%) due to OH scavenging

Dimer type	Observed m/z (−)	RT, min	Molecular formula	Error, ppm	O:C	$\bar{OS}$ _C^†	logC*,^‡ μg m⁻³	Exchangeable hydrogens	SOA mass fraction,^§^,^¶ %
1	323.1860	6.86	C₁₈H₂₈O₅	0.6	0.28	−1.00	−3.9	2	0.04−0.17
	355.1754	6.24	C₁₈H₂₈O₇	−0.8	0.39	−0.78	−7.6	4	0.11−0.36
	419.1525	4.70	C₁₈H₂₈O₁₁	−6.7	0.61	−0.33	−15.2	4	0.02−0.16
	373.1851	5.99	C₁₈H₃₀O₈	−2.9	0.44	−0.78	−9.4	4	0.07−0.23
	405.1764	4.49	C₁₈H₃₀O₁₀	0.7	0.56	−0.56	−13.2	5	0.06−0.62
	351.1828	5.73	C₁₉H₂₈O₆	5.7	0.32	−0.84	−6.1	2	0.10−0.41
	337.2027	7.16	C₁₉H₃₀O₅	3.6	0.26	−1.05	−4.3	2	0.46−2.01
	369.1916	6.48	C₁₉H₃₀O₇	0.8	0.37	−0.84	−7.9	4	2.23−9.24
2	341.1960	6.87	C₁₈H₃₀O₆	−1.2	0.33	−1.00	−5.7	2	0.06−0.24
	357.1919	6.91	C₁₈H₃₀O₇	1.7	0.39	−0.89	−7.6	3	0.39−1.60
	373.1851	5.70	C₁₈H₃₀O₈	−2.9	0.44	−0.78	−9.4	3	0.14−0.47
	389.1814	6.18	C₁₈H₃₀O₉	0.8	0.50	−0.67	−11.3	3	1.88−7.81
	353.1961	6.15	C₁₉H₃₀O₆	−0.8	0.32	−0.95	−6.1	3	0.14−0.60
3	315.1448	5.83	C₁₅H₂₄O₇	1.3	0.47	−0.67	−6.6	3	0.02−0.10
	347.1346	5.19	C₁₅H₂₄O₉	1.2	0.60	−0.40	−10.5	3	0.03−0.25
	375.1653	6.24	C₁₇H₂₈O₉	−0.5	0.53	−0.59	−11.0	3	0.02−0.24
	417.1769	6.76	C₁₉H₃₀O₁₀	1.9	0.53	−0.53	−13.5	2	0.06−0.62
	403.1963	6.28	C₁₉H₃₂O₉	−1.2	0.48	−0.74	−11.6	3	0.07−0.24
4	345.1549	5.36	C₁₆H₂₆O₈	0.1	0.50	−0.63	−8.8	2	0.05−0.50
	359.1714	5.89	C₁₇H₂₈O₈	2.2	0.47	−0.71	−9.1	3	0.32−1.07
	339.1822	6.34	C₁₈H₂₈O₆	4.1	0.33	−0.89	−5.7	2	0.46−1.93
	355.1754	5.27	C₁₈H₂₈O₇	−0.8	0.39	−0.78	−7.6	5	0.51−1.72
	371.1707	5.46	C₁₈H₂₈O₈	0.3	0.44	−0.67	−9.4	3	0.30−1.22

Dimers are grouped into four types based on structure and formation mechanism (see main text).

^{^†}

Average carbon oxidation state ( $\bar{OS}$ _C = 2 O:C − H:C).

^{^‡}

Saturation mass concentration (C*). Estimated using empirical model developed by Donahue et al. (35).

^{^§}

Calculated for β-pinene SOA produced from O₃-initiated oxidation in the CTEC (SI Appendix, Table S1, Exp. 1) after ∼4 h of reaction.

^{^¶}

Upper and lower bounds represent mass fraction estimates derived from experimental and computational approaches, respectively. Uncertainties in experimental and computational approaches are estimated to be ±23% (relative) and a factor of 3, respectively. Details are provided in SI Appendix, S7.