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Showing papers by "Lester Andrews published in 1976"


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the mechanism for trapping new chemical species by condensing the products of a microwave discharge with inert matrices and found that the major product species, HCl2 radical or anion, was formed under conditions where neither ions nor atomic species produced in the discharge were condensed in the matrix.
Abstract: The mechanism for trapping new chemical species by condensing the products of a microwave discharge with inert matrices has been investigated. Variation of geometrical, electrical, and chemical parameters of the Ar, HCl, Cl2 system indicated that the major product species—HCl2 radical or anion—was formed under conditions where neither ions nor atomic species produced in the discharge were condensed in the matrix. The mechanism for forming the product species is vacuum ultraviolet photolysis of the sample during deposition with radiation from the microwave discharge, since a coaxial orifice discharge tube provided photolysis and produced the product species, while studies with an off‐axis orifice discharge tube, which could not serve as a photolysis source, did not produce the product. The H atom–Cl2 reaction gave HCl using both discharge tubes, but the HClx2 species was produced only with the coaxial tube. Hence, this species requires vacuum ultraviolet light in addition to H and Cl atoms for its producti...

101 citations



Journal ArticleDOI
TL;DR: In this paper, the ground state potential function minima near the ionic excited state values for ground state KrF, XeF and XeCl were found to be near the RbF and CsF values.
Abstract: Argon matrix samples of Kr/F2, Xe/F2, Xe/Cl2, and Xe/Br2 have been photolyzed at 20 K. Emission spectra using uv excitation and uv absorption spectra following photolysis are assigned to the KrF, XeF, XeCl, and XeBr molecules. Vibrational spacings on two KrF and two XeF absorption bands are near RbF and CsF values, which supports the ionic model for the excited states. The vibronic KrF and XeF absorptions, and two very sharp XeCl bands, indicate ground state potential function minima near the ionic excited state values. This suggests that chemical bonding effects are significant in ground state KrF, XeF, and XeCl.

54 citations


Journal ArticleDOI
TL;DR: In this paper, the argon matrix reactions of alkali chloride salts with Cl2 have been investigated through infrared and Raman spectra, and it was shown that the Cl3− ions are asymmetric in these ion pairs.
Abstract: The argon matrix reactions of alkali chloride salts with Cl2 have been investigated through infrared and Raman spectra. In each infrared experiment, an intense product band was observed between 327 and 375 cm−1 and assigned to the antisymmetric stretching vibration ν3 of the Cl3− anion in the ion pair M+Cl3−. Raman spectra of these reaction mixtures yielded the same ν3 bands and, in addition, new signals between 253 and 276 cm−1 which are assigned to the symmetric stretching vibration ν1 of Cl3− in the M+Cl3− species. The observation of two stretching modes in the Raman spectra indicates that the Cl3− ions are asymmetric in these ion pairs. Bromine counterparts and the mixed chlorine–bromine anions were also formed, and used to verify that the anion in the M+X3− species contains three halogen atoms, with the metal ion beside the anion in an asymmetric ’’T’’ shaped structure.

51 citations





Journal ArticleDOI
TL;DR: In this article, the products of argon matrix reactions of alkali metal atoms and bromine and iodine have been studied optically in thin films on a sapphire window at 17 K.
Abstract: The products of argon matrix reactions of alkali metal atoms and bromine and iodine have been studied optically in thin films on a sapphire window at 17 K. The bromine reaction produced a strong band near 360 and a weak band near 640 nm, depending upon the alkali reagent, and the reactions with iodine gave a strong absorption near 380 and a medium intensity absorption near 680 nm. These bands are due to a+a* + and TI*+a* transitions, respectively, of the dihalide anions in the M x2 species. The small alkali metal effect on the transition energies is in accord with an ionic model of polarizable ion pairs, with the exception of cesium, which is capable of inner shell bonding and red-shifting the transitions from their expected positions. * The Author is a Sesquicentennial Associate on leave from the University of Virginia, and an Alfred P. Sloan Fellow. 0 0 ·J ' .{,Ji 11 0 7 5

23 citations


Journal ArticleDOI
TL;DR: In this paper, the matrix reactions of alkali bromide salts and HBr and DBr have been investigated in argon matrices, and it was shown that both type I and type II HClBr− anions exist and the resulting form may be determined by cation position.
Abstract: The matrix reactions of alkali bromide salts and HBr and DBr have been investigated in argon matrices. In each case, an intense band was observed from the reaction product, which was assigned to the antisymmetric stretch, ν3, of the HBr2− and DBr2− anions in the M+HBr2− and M+DBr2− ion pairs. Comparisons to literature spectra, in conjunction with quartic deuterium shifts, indicate that the anion has a linear, centrosymmetric geometry in the isolated ion pair. A less intense band was also observed which has been assigned to the combination band ν1+ν3 for the HBr2− anion. Reaction of alkali bromide salts with HCl and alkali chloride salts with HBr have been shown to yield identical absorptions for the M+HClBr− ion pairs. The spectra suggest that both type I and type II HClBr− anions exist, and the resulting form may be determined by cation position.

17 citations


Journal ArticleDOI
TL;DR: In this paper, the ultraviolet absorption spectra of Ar/Xe/O 3 matrix samples subjected to mercury-arc photolysis showed a marked decrease in ozone absorption at 250 nm and a weak new band at 227 nm.

13 citations


01 Jan 1976
TL;DR: In this article, the authors investigated the mechanism for trapping new chemical species by condensing the products of a microwave discharge with inert matrices and found that the major product species, HCl2 radical or anion, was formed under conditions where neither ions nor atomic species produced in the discharge were condensed in the matrix.
Abstract: The mechanism for trapping new chemical species by condensing the products of a microwave discharge with inert matrices has been investigated. Variation of geometrical, electrical, and chemical parameters of the Ar, HCl, Cl2 system indicated that the major product species—HCl2 radical or anion—was formed under conditions where neither ions nor atomic species produced in the discharge were condensed in the matrix. The mechanism for forming the product species is vacuum ultraviolet photolysis of the sample during deposition with radiation from the microwave discharge, since a coaxial orifice discharge tube provided photolysis and produced the product species, while studies with an off‐axis orifice discharge tube, which could not serve as a photolysis source, did not produce the product. The H atom–Cl2 reaction gave HCl using both discharge tubes, but the HClx2 species was produced only with the coaxial tube. Hence, this species requires vacuum ultraviolet light in addition to H and Cl atoms for its producti...