Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information ABSTRACTWe report spectroscopic observations on B atoms isolated in cryogenic parahydrogen (pH 2 ), normal deuterium (nD 2 ), Ne, Ar, Kr, and Xe matrices, and of B 2 molecules in Ne, Ar, Kr, and Xe matrices. The 2s 2 3s( 2 S) *--2s 2 2p( 2 P) B atom Rydberg absorption suffers large gas-tomatrix blue shifts, increasing from +3000 to +7000 cm-1 in the host sequence: Xe < Kr < Ar t Ne z nD 2 t pH 2 . Much smaller shifts are observed for the 2s2p 2 ( 2 D) +-2s 2 2p( 2 P) B atom coreto-valence transition. We assign pairs-of absorption peaks spaced by • 10 nm in the 315 to 355,*4 -------)egion to the B 2 (A 3Z," < X 3 Zg-) Douglas-Herzberg transition. We assign a much weaker 1•q'i,# progression in the 260 to 300 nrm region to the B 2 (2) l' --X + Z transition. We report a nove progression of strong peaks in the 180 to 200 nm region which we suspect may be due to B 2 molecules, but which remains unassigned. Ultraviolet (UV) absorption spectra of B/pH 2 solids show two strong peaks at 216.6 and 208.9 nm, which we assign to the matrix perturbed 2s 2 3s( 2 S) +-2s22p( 2 P) and 2s2p 2 ( 2 D) <-2s 2 2p( 2 P) B atom absorptions, respectively. This assignment is

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The results of matrix isolation experiments on carbon atoms and clusters generated by pulsed laser ablation of graphite are presented. C3 and other Cn clusters are observed by their infrared absorptions in Ne, ortho-D2, and para-H2 matrices. CH4 molecules and CH3 radicals are observed in H2 matrices, as are CD4 molecules in D2 matrices. The CH4:C3 concentration ratio in the H2 matrices is seen to increase dramatically with increasing ablation laser intensity. These results confirm and illuminate previous work by Miki, Wakabayashi, Momose, and Shida [J. Phys. Chem. 100, 12135 (1996)] on Cn doped cryogenic para-H2 samples produced by combined laser ablation and gas condensation in an enclosed cell. Their nonobservation of any hydrocarbon reaction products (particularly CH4) is explained by the lower intrinsic absorption strengths of the CH4 vs C3 vibrational transitions, and by attributing a low C1:C3 production ratio to the ablation process under their laser intensity and wavelength conditions.

Articles you may be interested inA simple but accurate potential for the naphthalene-argon complex: Applications to collisional energy transfer and matrix isolated IR spectroscopy Visible laser excitation (460-725 nm) of dilute rare gas/12 (2000: 1) matrices resulted in emission from the lzA 3TI ( 1 u ) state. Reanalysis of the A.-X spectra provided revised molecular constants for matrix isolated 1 2 , A state lifetimes of 70 ± 20, 80 ± 20, and 110 ± 30 f.Ls were observed in Ar, Kr, and Xe hosts, respectively. Excitation spectra for the A state closely followed the 12 continuum absorption spectrum, indicating that transfer from the B 3TI(Ou+) and ITI(1u) states was effective in populating Iz(A). At dilution ratios of 600: 1 or lower the I 2 P 1/2 _2 P 3/2 transition was observed in conjunction with the A-X bands. Excitation studies showed that isolated I atoms, trapped during the deposition process, were excited by energy transfer from nearby If molecules. A vibronic progression, similar to the A-X bands, but shifted to longer wavelengths, was noted in concentrated Rg/lz (300: 1) matrices. This system, which was emitted with a lifetime of about 10 ms, most probably originated from perturbed 12 A' 3TI(2 u )' Intermolecular energy transfer was observed in matrices that contained 12 codeposited with 02' Electronic excitation of I z resulted in a long-lived emission from O 2 a I Ll g • Matrices containing high concentrations of iodine also exhibited 02(a) .-1(2p II 2 ) transfer. . R FI G. 1. Approximate potential energy curves for selected low-energy electronic states of 1 2 , 674