O(3PJ) formation and desorption by 157-nm photoirradiation of amorphous solid water.

Photodissociation of amorphous solid water (ASW) deposited on a thinly oxidized copper substrate at 82 K was studied by measuring O((3)PJ=2,1,0) photoproducts detected with resonance-enhanced multiphoton ionization. For each spin-orbit state, the oxygen atom time-of-flight spectrum was measured as a function of H2O exposure, which is related to ice thickness, and 157-nm irradiation time. Four Maxwell-Boltzmann distributions with translational temperatures of 10,000 K, 1800 K, 400 K, and 82 K were found to fit the data.

Mechanisms of H2O desorption from amorphous solid water by 157-nm irradiation: an experimental and theoretical study.

The photodesorption of water molecules from amorphous solid water (ASW) by 157-nm irradiation has been examined using resonance-enhanced multiphoton ionization. The rotational temperature has been determined, by comparison with simulations, to be 425 ± 75 K. The time-of-flight spectrum of H2O (v = 0) has been fit with a Maxwell-Boltzmann distribution with a translational temperature of 700 ± 200 K (0.

Photodissociation of methyl iodide adsorbed on low-temperature amorphous ice surfaces.

Photodissociation dynamics of methyl iodide (CH3I) adsorbed on both amorphous solid water (ASW) and porous amorphous solid water (PASW) has been investigated. The ejected ground-state I((2)P3∕2) and excited-state I((2)P1∕2) photofragments produced by 260- and 290-nm photons were detected using laser resonance-enhanced multiphoton ionization. In contrast to gas-phase photodissociation, (i) the I((2)P3∕2) photofragment is favored compared to I((2)P1∕2) at both wavelengths, (ii) I((2)P3∕2) and I((2)P1∕2) have velocity distributions that depend upon ice morphology, and (iii) I2 is produced on ASW.