Showing papers by "Lester Andrews published in 1978"

Matrix reactions of magnesium atoms with ozone. Infrared spectra of MgO, MgO2, and MgO3 in solid nitrogen

Abstract: The magnesium–ozone reaction has been studied by condensing the reagents with nitrogen at 14 K. Isotopic substitution with 26Mg, 16,18O3, and 18O3 has identified infrared absorptions due to two different Mg+O−3 species, MgO2 and MgO. Six isotopic MgO molecules support this infrared detection of MgO which shows a blue matrix shift. Analogous argon matrix reactions produced only Mg+O−3 and two isomeric MgO3 species.

Matrix radiolysis and photoionization of CF2Cl2 and CF3Cl. Infrared spectra of CF2Cl+ and the parent cations

Abstract: The ’’Freon’’ molecules CF2Cl2 and CF3Cl have been subjected to matrix radiolysis and photoionization during condensation with excess argon at 15 K. Infrared spectra showed stable and free radical products and new absorptions due to charged species. The molecular ion bands exhibited different behavior on filtered mercury arc photolysis. New 1415 and 1515 cm−1 absorptions decreased by 220–1000 nm photolysis are assigned to CF2Cl+2 and CF3Cl+. Other absorptions eliminated by mercury arc light, some of which were produced on photolysis of sodium–chlorofluoromethane samples, are attributed to molecular anions. The vibrational assignments were verified by carbon‐13 isotopic studies.

Spectral Evaluation of Windowless Argon Discharge Vacuum Ultraviolet Lamps for Matrix Isolation Spectroscopy

Abstract: Windowless argon discharge tubes used as resonance lamps in matrix isolation experiments produced strong argon resonance radiation at 1048 and 1067 A, and at low pressures, the Ar+ resonance doublet at 920 and 932 A made a major contribution to the vacuum ultraviolet spectrum. At discharge pressures below 60 μ, the relative intensities of the 1048, 1067 A argon resonance doublet are reversed in favor of the 1067 A line, although the Ar+ resonance lines are substantially increased relative to the neutral atom emissions.

One‐photon and consecutive two‐photon excitation of Ca2 fluorescence in solid krypton at 12 K

Abstract: Laser‐excited emission from the Ca2 van der Waals dimer isolated in solid krypton has been studied. Analysis of the strong red emission at 14 000 cm−1 gives ωe″=80 cm−1, ωex″e=0.35 cm−1 for the ground state molecule. Observation of unrelaxed emission up to v′=7 and anti‐Stokes emission due to sequential two‐photon excitation are discussed in terms of excited and ground state vibrational relaxation rates. Resonance Raman scattering from Ca2 at Δν=80, 158, and 236 cm−1 was also observed.

Matrix radiolysis and photoionization of CFCl3. Infrared spectra of CFCl+2 and the parent cation

Abstract: The ’’Freon’’ compound CFCl3 has been subjected to radiolysis and photoionization during condensation with excess argon at 15 K. Infrared spectra of the matrix samples identified stable and free radical products and new absorptions which are attributed to charged species. The molecular ion bands exhibited three different behavior patterns on filtered mercury arc photolysis: The most photosensitive bands, destroyed by 420–1000 nm light, are assigned to the parent cation; several absorptions which photodissociated with 290–1000 nm radiation are due to a molecular anionic species; and new bands reduced by 220–1000 nm light are assigned to the daughter cation CFCl+2. The vibrational assignments were confirmed by carbon‐13 substitution.

Laser-excited fluorescence of calcium dimer in inert gas matrices

Abstract: A strong, red, laser‐excited fluorescence has been observed for Ca2 in inert gas matrices. Band origins were located using calcium‐44 substitution and the spectroscopic constants were determined for the ground state van der Waals molecule in several different sites in solid argon and one site in solid xenon. Spectroscopic constants for the Ca2 excited state in solid neon (ω′e=118±2, ωex′e=0.3±0.1, and T0–0=15 150±20 cm−1) provide an estimate for the yet to be determined gas‐phase constants for the upper state of this red transition. The observation of both unrelaxed and relaxed emission from Ca2 depending on the site and matrix is discussed in terms of guest–host interaction.

Absorption spectra of heteronuclear group II metal diatomic molecules in solid argon at 10 K

Abstract: Codeposition of different group IIA and IIB metal atoms in rare gas matrices at 10 K has resulted in the identification of several previously unreported diatomic species from their electronic absorption spectra. Structured absorption bands were observed for ZnHg, CdHg, MgZn and MgCd at 258, 266, 318, and 327 nm, respectively, with average vibronic spacings of 85, 81, 146, and 144 cm−1, respectively, Unstructured absorptions were observed at 267 and 318 nm for Zn/Cd and Mg/Hg combinations. Spectroscopy and bonding are discussed in terms of simple molecular orbital models. The Hg2 dimer is considered in light of the ZnHg and CdHg data.

Ultraviolet‐laser induced fluorescence of UF6 isolated in argon matrices

Abstract: Fluorescence spectra of UF6 isolated in solid argon at 12 K and excited at 350.7, 356.4 nm have been studied as a function of concentration. The spectra indicate substantial solute–solute interaction for Ar/UF6 ratios less than 800/1. The most dilute samples, Ar/UF6=1800/1, gave strong sharp progressions in the ν5 (T2g) mode, weaker series in the ν1 (A1g) mode and strong combination progressions of ν1 and ν5 with the ν6 (T2u) mode of the UF6 molecule. At higher solute concentrations, vibrational structure is coalesced into a broad series of bands spaced 200±20 cm−1 apart. The vapor phase, matrix isolation and solid UF6 fluorescence spectra are compared.

Absorption spectra of matrix-isolated alkaline earth metal diatomic molecules

Abstract: Mg, Ca, and Sr atoms were codeposited with argon and krypton at 10 K for optical absorption investigation of the van der Waals diatomic molecules. Very strong and weak structured absorptions were observed for Mg2 at 367 and 444 nm, respectively. An unstructured 507 nm and a strong structured 648 nm absorption were found for Ca2, and a strong structured 710 nm absorption was observed for Sr2. Intermediate absorptions with intermediate spacings were observed for CaMg, SrMg, and SrCa in mixed‐metal experiments. The strong absorptions are assigned to 1Σ+u(1S+1P) ←1Σ+g(1S+1S) transitions.