Showing papers by "Lester Andrews published in 1981"

Magnetic circular dichroism spectra of alkaline earth metal atoms, dimers, and aggregates in noble gas matrices

Abstract: The magnetic circular dichroism (MCD) of Mg, Ca, and Sr atoms, dimers, and higher aggregates have been studied after codeposition with noble gases at low temperatures. The1Σ+g→1Πu transition in each of the M2 species (M = Mg, Ca, Sr) occurring to the blue of the 1S→1P resonance transition, is unambiguously identified by measurement of the excited state magnetic moment. The distinct band at ∼30,000 cm−1 in magnesium samples is identified as Mg3, and the measured excited state magnetic moment favors the assignment, 1A1′→1E′, corresponding to an equilateral triangular (D3h) geometry. A broader band at ∼33 000 cm−1 in Ar is assigned to Mg4, and the very small excited state magnetic moment is consistent with the assignment, 1A1→1T2, of a tetrahedral species. In Ca/Ar, Ca/Kr, and Sr/Ar matrices, the 1S→1D atomic transition is seen with about 5% of the intensity of the corresponding 1S→1P transition. The accompanying MCD patterns unambiguously demonstrate the presence of two distinct sites for Ca atoms and three distinct states for Sr atoms. Furthermore, the fact that the 1S→1D ? terms are opposite in sign to those for 1S→1P together with a consideration of the probable structure of the noble gas lattices suggests that these sites have approximate D3h symmetry. It is clear that application of the MCD technique to systems trapped in matrices provides a rather unique means for characterizing the species present and can give considerable information about the matrix environment in which the species are located.

Matrix spectroscopic studies of chlorine atom-ozone reaction products

Abstract: A spectroscopic study is presented of the matrix-isolated products of the direct combination reaction of chlorine atoms with ozone and of the microwave discharge reaction of chlorine and oxygen. Infrared spectra in the wavenumber range 2000 to 200 per cm were recorded for reaction products trapped by the condensation of a matrix of solid argon. Evidence for the formation of the ClO radical as well as the ClOO and ClClO radicals during the direct chlorine-ozone reaction is obtained, however no evidence is found for the presence of asymmetric ClO3 under conditions thought favorable for its formation. The ClO molecule is also observed following the microwave discharge reaction of chlorine and oxygen in argon in the isotopic forms (Cl-35)(O-16), (Cl-37)(O-16), (Cl-35)(O-18), and (Cl-37)(O-18). It is noted that the vibrational frequency for the (Cl-35)(O-16) radical at 849.2 per cm is blue-shifted 5 per cm above its gas-phase fundamental.

Matrix spectroscopic studies of chlorine atom-ozone reaction products

Abstract: A spectroscopic study is presented of the matrix-isolated products of the direct combination reaction of chlorine atoms with ozone and of the microwave discharge reaction of chlorine and oxygen. Infrared spectra in the wavenumber range 2000 to 200 per cm were recorded for reaction products trapped by the condensation of a matrix of solid argon. Evidence for the formation of the ClO radical as well as the ClOO and ClClO radicals during the direct chlorine-ozone reaction is obtained, however no evidence is found for the presence of asymmetric ClO3 under conditions thought favorable for its formation. The ClO molecule is also observed following the microwave discharge reaction of chlorine and oxygen in argon in the isotopic forms (Cl-35)(O-16), (Cl-37)(O-16), (Cl-35)(O-18), and (Cl-37)(O-18). It is noted that the vibrational frequency for the (Cl-35)(O-16) radical at 849.2 per cm is blue-shifted 5 per cm above its gas-phase fundamental.