Table 1.

State-of-the-art measurement techniques for the detection of ambient HOx, ROx and NO₃ radicals worldwide.

Techniques	Species	Principle	Chinese groups	International groups
LIFd	OH, HO2	OH: OH + hν(308 nm) → OH*→ hν HO2: HO2+NO→OH followed by LIF detection of OH	PKU	FZJ, MPI, Leeds, Lille, PSU, Indiana, JAMSTEC
	RO2	RO2(+CO/NO)→HO2a followed by LIF detection of HO2	–	FZJ, Leeds
	NO3	NO3 + hν(623 nm) → NO3*→ hν	–	TMU [16]e
CIMSd	OH	OH+34SO2+M→H34SO3;	CAS (DICP) [17]	DWD, NUIG, Helsinki, CNRS, Colorado
		H34SO3+O2→34SO3+HO2,
		34SO3+H2O→H234SO4;
		H234SO4+NO3−ċHNO3→H34SO3−ċNO3+HNO3
	HO2, RO2	RO2/HO2(+NO/SO2)→ H2SO4b followed by CIMS detection of H2SO4	HKPoly	DWD, Helsinki, CNRS, Colorado, GIT [18]
DOASd	OH	OH + hν(308 nm) → OH*	–	FZJ, Frankfurt Univ [19]
	NO3	NO3 + hν(623–662 nm) → NO3*	CAS (AIOFM) [20]	California [21]
CEAS	NO3	NO3 + hν(662 nm) → NO3*	PKU [22], CAS (AIOFM) [23]	NOAA [24], Cambridge [25], MPIC [26], Cork [27], UEA [28]
CRDs	ROx*	RO2/HO2(+CO/NO)→NO2c followed by CRDs/CEAS detection of NO2	CAS (AIOFM) [29]	Bremen [30]

^aRO₂+NO→HO₂; HO₂+NO→OH; OH+CO→HO₂.

^bRO₂+NO→HO₂; HO₂+NO→OH; OH+SO₂→HO₂+H₂SO₄.

^cNO+RO₂→HO₂+NO₂; NO+HO₂→OH+NO₂; OH+CO→HO_2.

^dRevised version according to the report of the International HOx Workshop 2015 [31].

^eNot applied in the field so far.

FZJ, Forschungszentrum Juülich; MPIC, Max-Planck Institute for Chemistry, Mainz; Leeds, University of Leeds; Lille, Universiteé de Lille; PSU, Pennsylvania State University; Indiana, Indiana University; JAMSTEC, Japan Agency for Marine-Earth Science and Technology; TMU, Tokyo Metropolitan University; DWD, German Meteorological Service; NUIG, National University of Ireland Galway; Helsinki, University of Helsinki; CNRS, The National Center for Scientific Research (Orleans); Colorado, University of Colorado; GIT, Georgia Institute of Technology; Frankfurt Univ, University of Frankfurt; California, University of California; NOAA, National Oceanic and Atmospheric Administration; Cambridge, University of Cambridge; Cork, University of Cork; UEA, University of East Anglia; Bremen, University of Bremen.