Luminescence from UV-Irradiated Amorphous H₂O Ice

Abstract

The luminescence emitted by amorphous H2O ice at 78 K when irradiated with a continuous source of 260 nm light has been examined. The emission spectrum was similar to that from crystalline ice, exhibiting two features around 340 and 420 nm that had short and long lifetimes, respectively. The rise and fall times of the 420 nm band were the same within experimental error, and the decay was equally well fit by either a biexponential decay or a second-order decay with initial concentrations in a ratio of 3.2:1. However, the identical nature of the luminescence rise and decay profiles strongly suggests biexponential kinetics. The 420 nm emission was tentatively attributed to the 4Σ- → X2Π transition of excited OH radicals. A reaction mechanism that explains the preceding observations is presented, and the biexponentiality of the 420 nm decay is attributed to excited OH radicals located in two distinct environments within the ice lattice.

Photolysis and radiolysis of water ice on outer solar system bodies

“…These reactions often lead to an electronically excited product which emits a photon, a process called chemiluminescence. Recent laboratory studies [Quickenden et al, , 1996Vernon et al, 1991;Miyazaki et al, 1992;Matich et al, 1993] suggest that the prime candidates for luminescence emission are OH, 02, and occasionally H [Bakker et al, 1988; Quickenden et al, 1988]. Of these species, OH is the best known emitter.…”

“…However, for materials in space the solar spectrum increases steeply with increasing wavelength, so that in order to see, for instance, the 0.34/am luminescence band excited by the solar flux at wavelengths short of -0.26/am would require quantum efficiencies •>0.1 to cause the reflected light to be enhanced by 20% due to the presence of the luminescence. Typical quantum etficiencies for electron irradiated ice are -10 -5 , although much higher values may occur, e.g., for the 0.34/am band excited by -0.26/am UV radiation [Quickenden et al, 1996]. Therefore the main limitation for space observations is the intense reflected sunlight which will mask the luminescence, usually occurring in the brighter region of the solar spectrum.…”

Luminescence of superdispersed systems by the example of KBr:Tl. Part 1

“…Emission in this spectral region can be connected not only with particular centers with disturbed structure containing thallium, but also with intrinsic defects of host material and OH − radicals. For example, a broad luminescence band, ascribed to OH − radicals was observed in paper [19] under excitation in the band 4.76 eV, i.e., at excitation at a low-energy absorption edge of A band of our samples. It also possible to suppose that some bands in the low-energy region of the luminescent spectra of our samples are connected with intrinsic defects of host material.…”

Surface Natrotantite Phase Induced Efficient Charge Carrier Separation and Highly Active Surface of TaON for Superior Enhanced Photocatalytic Performance

“…[ 30 ] Therefore, the more negative V fb values compared to that of pristine TaON suggests the higher gradient potential in space charge layer, in which the photogenerated charge carriers will be separated much easier. Otherwise, the V fb values of TaON (3) All the spectra can be well fi tted using biexponential function as follows [ 31 ] exp exp…”