Quantum yields for the production of O(1D) from photodissociation of O2 at 1160–1770 Å

Abstract

The quantum yield for the production of O(1D) by photodissociation of O2 was measured in the 1160–1770 Å wavelength region. For wavelengths longer than 1390 Å, the quantum yields are unity and constant, with a sharp cutoff at about 1750 Å. For wavelengths shorter than 1390 Å, the O(1D) quantum yields depend strongly on wavelength. The positions of many of the structures correspond to Rydberg states identified by various authors, and the data show by which of the two principal dissociative channels, O(3P)+O(3P) or O(1D)+O(3P), the excited molecules predissociate. The total oxygen atom yields were also measured and clearly show that all photon absorption leads to dissociation in the spectral region studied. Possible identification of absorption to the 3Πu valence state has been made, with a peak at 1356 Å (9.14 eV).

Methanol Formation via Oxygen Insertion Chemistry in Ices

“…The convolution of lamp intensity, sapphire transmittance, and absorption crosssection for each species is shown as the "effective" crosssection in Figure 1b still has a large absorption profile which is dominated by the 160.8nm Lyman band of the H 2 D 2 lamp. The photoproducts of O 2 in this wavelength regime are wellcharacterized: upon exposure to light at wavelengths from 140-175nm, O 2 dissociates into O( 3 P) + O( 1 D) with an efficiency of unity (Lee et al 1977).…”

“…As mentioned in Section 1, for the UV wavelengths in this study, O 2 dissociation proceeds through the channel O 2 → O( 1 D) + O( 3 P) with an efficiency of unity (Lee et al 1977). Thus, our ices should contain equal parts O( 1 D) and O( 3 P).…”

“…O( 1 D) production has been demonstrated by UV photolysis of a number of molecules which should be abundant in interstellar ice mantles, including O 2 , CO 2 , O 3 , and H 2 O, as well as electron impact of O 2 and CO 2 (Lee et al 1977;Slanger & Black 1971;DeMore & Raper 1966;Stief et al 1975;Cosby 1993;Kedzierski et al 2013). CO 2 and H 2 O are of particular importance, as H 2 O is the main constituent of interstellar ices and CO 2 is typically present at abundances of ∼10-30% with respect to H 2 O (Öberg et al 2011).…”

Response to “Comment on ‘Ab initio dynamic dipole polarizabilities for O2, its photoabsorption spectrum in the Schumann–Runge region, and long-range interaction coefficients for its dimer’ ” [J. Chem. Phys. 111, 11236 (1999)]

“…4 and the above comment͒ while we had calculated a value of only 0.022. Even for such a small value a relative error of about 2-3 seems really disturbing.…”

Comment on “Ab initio dynamic dipole polarizabilities for O2, its photoabsorption spectrum in the Schumann–Runge region, and long-range interaction coefficients for its dimer” [J. Chem. Phys. 109, 9802 (1998)]

“…The many optical and electron-impact measurements of the SR continuum, reviewed by Chan et al, 12 have led to a knowledge of the corresponding oscillator-strength density to an accuracy of ϳ3%. In addition, the measurement of fluorescence-excitation cross sections 13,14 has enabled decomposition of the continuum into constituent parts due to the…”