Hydroxyl Radical Concentrations Measured in Ambient Air

Abstract

Diurnal variations in the hydroxyl radical concentration of ambient air were measured for the first time by the technique of laser-induced fluorescence.

Identification of intermediate radicals in theCH4microwave plasma by theLi+Fujii1, Syouji2 1992Phys. Rev. A221110View full textAdd to dashboardCite

“…By providing a means of detecting intermediate radicals in gaseous systems, the present method can be of immediate help in the study of combustion processes, chemical vapor deposition plasma treatment processes, and atmospheric reactions, in which OH and 02H figure prominently as an intermediate product [11]. It should also be noted that there are a number of ways in which the ion attachement technique for the radical detection can be improved at little cost in complexity, chiefly by substituting Na+, K+, Rb+, Cs+, Al+, Ag+, Ga+, and Fe+ for the present Li+ species.…”

The application of analytical techniques to the understanding of chemical processes occurring in the atmosphere†

“…These measurements are very important since they show that transient species, such as OH radicals are definitely present in the atmosphere and are not just figments of the imagination. Higher levels of OH radicals have been reported by other workers, notably Wang et al 30 radicals/cc, but it is most likely that their measurement technique produced artifacts. More recent indirect measurements by Campbell 31 and by Voltz et al 32 who measured the carbon-13 isotope level in atmospheric CO 2 , tend to confirm the lower numbers.…”

Fluorescence Methods

“…The false OH concentration is proportional to the square of the excitation power and linear in ozone and water vapour number density. Early attempts (Wang & Davis, 1974;Wang et al, 1975Wang et al, , 1976Davis et al, 1976) to measure tropospheric OH by LIF detected only laser-generated OH.…”

“…This is superior to excitation at 282 nm because the product of the ozone absorption cross section and the photolysis quantum yield of O 1 D is reduced by a factor of ∼ 30 at 308 nm relative to 282 nm. Early instruments for tropospheric OH detection Wang and Davis, 1974;Wang et al, 1975Wang et al, , 1976) failed due to lasergenerated OH. Hard and co-workers (1984) reduced laser-generated OH using FAGE, as described in Section 2.2.5, and their early success combining FAGE with excitation at 308 nm using high repetition-rate lasers has been adopted as a model by most research groups using LIF to observe tropospheric OH (Creasey et al, 1997;Faloona et al, 2004;Hard et al, 1995;Holland et al, 1995;Kanaya et al, 2001).…”