George R. Smith

Matrix‐isolation triplet (T1) state IR spectroscopy of acridine and phenazine

The matrix‐isolated infrared (IR) spectra of the lowest triplet (T1) states of acridine and phenazine have been obtained by direct measurement. Population of T1, sufficient for IR detection, is achieved by pulsed indirect pumping with an Ar+ laser source. The ground and triplet state IR spectra were 180° out of phase, providing unambiguous indentification of the excited metastable state absorptions. Approximate T1 vibrational assignments are made on the basis of analogous experimental and theoretical results for ground state acridine, phenazine, and anthracene.

Spectroscopy of the thermal oxidation of NO in solid oxygen at cryogenic temperatures

Abstract It has been found that nitric oxide can be isolated in solid oxygen at temperatures of about 13 K. Annealing the film to ∼35 K allows the formation of cis -(NO) 2 , which, after recooling, is observed to react slowly with the O 2 matrix to form iso-N 2 O 4 . The spectroscopy of this system is discussed in this article. In particular, vibrational frequencies are given for both 14 N and 15 N isomers of NO, cis -(NO) 2 , D 2 h -N 2 O 4 , iso-N 2 O 4 , and N 2 O 5 isolated in the oxygen matrix. Other species present in these experiments are two isomers of N 2 O 3 , and several unidentified species which are suggested to be different forms of N 2 O 4 . The possible presence of an isomer of NO 3 is also discussed.

The infrared spectrum of matrix isolated hydrogen and deuterium

The induced infrared spectra of H2 and D2, trapped in matrices of Ar, Kr, N2, CO, have been investigated. It is found that in Ar and Kr, the pure rotation spectrum is always readily observable. Portions of the fundamental region, however, are induced by impurities, while the entire spectrum is impurity induced in N2 matrices. These results are discussed in light of a recent Raman study of this system, and in comparison with several single crystal studies. Effective rotational and vibrational constants for matrix isolated H2 are also given.

Note on absorptions due to H2, HD, and D2 in argon matrices

The infrared spectra of matrix isolated D2, HD, and H2 are reported. The differences in the spectra of D2, HD, and H2 are discussed in terms of symmetry of a molecule. (AIP).

The infrared and visible absorption spectra of the lowest triplet state of acridine isolated in an argon matrix

Abstract The infrared and visible absorption spectra of the lowest 3ππ* state of acridine, produced via cw laser pumping of an argon matrix isolated sample are reported. The visible spectrum agrees well with previous studies. In the infrared, absorptions of the triplet state are observed at 1434, 1104, 1048, 1004 and 751 cm−1.

The photochemistry of the matrix-isolated dichloroethylenes

Abstract The vacuum ultraviolet photolysis of the three isomers of dichloroethylene has been studied in argon, carbon monoxide, nitrogen and krypton matrices at 13 K. Selective excitation into various regions from 1200 to 2050 A with resonance line sources and a medium pressure Hg lamp resulted in the formation of HCl and chloroacetylene as the major products detected by infrared spectroscopy. Isomerization among the three dichloroethylenes was also important, while the production of acetylene and dichloroacetylene made only minor contributions to the photochemistry. The chlorovinyl radical was not identified, though several unassigned absorptions were observed. The infrared absorptions of chloroacetylene and HCl produced by photolysis of trans -1,2-dichloroethylene were shifted from those produced from the other isomers, providing evidence for αα elimination of HCl from the trans isomer. The effects of varying the matrix material from Ar to CO, N 2 or Kr show that all the processes, with the exception of the formation of acetylene and Cl 2 , arise from triplet states. It is suggested that the αα elimination process observed for the trans isomer is due to the participation of a 3 nσ * state in the photochemistry of this isomer.

Infrared laser photolysis: a new tool for the study of prebiotic chemistry.

Infrared laser induced dielectric breakdown and multiphoton absorption experiments on CH4/NH3 ‘atmospheres’ are described. It is found that HCN, a central intermediate in prebiotic chemistry, is a principle product. This, combined with the fact that dielectric breakdown appears to have much in common with ordinary electric sparks, suggests that the laser could be a useful tool in studies of prebiotic chemistry. Several possible experiments in this vein are suggested.

Laser-induced temporal and wavelength resolved spectroscopy of the 2Σ−-2Π and 2Δ-2Π systems of CH and CD isolated in rare gas matrices

Abstract The relaxation dynamics of matrix isolated CH and CD have been studied using laser-induced time and wavelength resolved spectroscopy. Vibrationally relaxed B (0′-0″) fluorescence occurs following laser excitation both above and below the gas phase dissociation limit. The vibrational relaxation rate in the B state of CH is found to be 4.6 × 10 6 sec −1 while the corresponding rate in CD is 5.7 × 10 5 sec −1 . The primary accepting mode in the relaxation process is consistent with rotation.