Products and yields from O3 photodissociation at 1576 Å

Abstract

An analysis has been made of the primary atomic and molecular products arising from O3 photodissociation at 1576 Å. The yield of oxygen atoms is 1.90±0.30, of which 71% are O(3P) and 29% are O(1D). Since a primary yield greater than unity can only be a consequence of three-fragment dissociation, these results suggest that fragmentation into three O(3P) atoms, and production of O(1D) plus a singlet oxygen molecule, have comparable yields. Observation of prompt emission in the 7300–8100 Å spectral region indicates that the singlet O2 is O2(b 1∑+g). Vibrational levels in the range v=0–6 have been detected, the distribution corresponding to a vibrational temperature of 104 K. This study is the first to show photodissociative production of the O2(b 1∑+g ) state in any system.

Collisional removal of O2(b 1Σg+,v=1,2) by O2, N2, and CO2

“…We calculate the b -X 4-0 Franck-Condon factor to be smaller than that for b -X 1-0 by a factor of 6ϫ10 4 . Alternative methods exist for generating a range of O 2 (b 1 ⌺ g ϩ ) vibrational levels, 48,49 which we intend to pursue.…”

Photodissociation of ozone at 193 nm by high-resolution photofragment translational spectroscopy

“…In this region there are the overlapping contributions of channel 3 and 4 from primary 0 atoms and channel 1 and 2 from 0 2 fragmentation. In an attempt to obtain a ''clean" primary 0 atom TOF spectrum, we recorded the spectrum of mje 8 (o++) at the same angle (Fig. 5), since primary 0 atoms are much more likely to appear as doubly charged ions than are fragments of 0 2 • Unfortunately, the 0 2 fragmentation contribution is still present, even if it is strongly decreased.…”

“…The reason for this is that despite the central importance of ozone in the stratosphere, the solar flux at 193 nm is low enough that dissociation there was considered unimportant. Taherian and Slanger [8] studied ozone photodissociation in a cell at 157 nm and reported a large yield of 0 2 ( b 1 L;:) as well as a quantum yield of 0.5 for dissociation into three ground state 0 atoms. Ravishankara and coworkers [9] performed a detailed cell experiment at both 222 and 193 nm, and despite the fact that they measured only oe P) or OH as a function of time and buffer gas concentration, they were able to infer a significant yield of 0 2 ( b 1 L;:) at 193 nm, a larger yield of triplet products than seen elsewhere in the Hartley band, and some triple dissociation.…”

“…The final difficulty with assignment of these as 0( 1 S) is a study by Taherian and Slanger. [8] This work placed an upper limit of .1% on 0(18) yield fr-om ozone photolysis in the range from 120 to 240 nm. We observe a branching fraction of > 4% for the total of these two channels.…”

Airglow on Mars: Some model expectations for the OH Meinel bands and the O IR atmospheric band

“…Values for the O 3 photoabsorption cross sections have been taken from Ogawa and Cook (1958): 526-1305 Å; Ackerman (1971Ackerman ( ): 1310Ackerman ( -1780Sander et al (2003Sander et al ( ): 1794Sander et al ( -2286Burrows et al (1999): 2300-7940 Å; Voigt et al (2001): 7940-8500 Å. O 3 photoionization and photodissociation quantum yields have been obtained from Taherian and Slanger (1985), Turnipseed et al (1991), Hancock and Tyley (2001), Bauer et al (2000), Wine and Ravishankara (1982), Brock andWatson (1980), Fairchild et al (1978), and Okabe (1978).…”