Showing papers by "Lester Andrews published in 1991"

Reactions of boron atoms with molecular oxygen. Infrared spectra of BO, BO2, B2O2, B2O3, and BO−2 in solid argon

Abstract: Boron atoms from Nd:YAG laserablation of the solid have been codeposited with Ar/O2 samples on a 11±1 K salt window. The product infrared spectrum was dominated by three strong 11B isotopic bands at 1299.3, 1282.8, and 1274.6 cm− 1 with 10B counterparts at 1347.6, 1330.7, and 1322.2 cm− 1. Oxygen isotopic substitution (16O18O and 18O2 ) confirms the assignment of these strong bands to ν3 of linear BO2. Renner–Teller coupling is evident in the ν2 bending motion. A sharp medium intensity band at 1854.7 has appropriate isotopic ratios for BO, which exhibits a 1862.1 cm− 1 gas phase fundamental. A sharp 1931.0 cm− 1 band shows isotopic ratios appropriate for another linear BO2 species; correlation with spectra of BO− 2 in alkali halide lattices confirms this assignment. A weak 1898.9 cm− 1 band grows on annealing and shows isotopic ratios for a BO stretching mode and isotopic splittings for two equivalent B and O atoms, which confirms assignment to B2O2. A weak 2062 cm− 1 band grows markedly on annealing and shows isotope shifts appropriate for a terminal–BO group interacting with another oxygen atom; the 2062 cm− 1 band is assigned to B2O3 in agreement with earlier work. A strong 1512.3 cm− 1 band appeared on annealing; its proximity to the O2 fundamental at 1552 cm− 1 and pure oxygen isotopic shift suggest that this absorption is due to a B atom–O2 complex.

Infrared spectra and structures of isotopically enriched sulfur (S3 and S4) in solid argon

Abstract: Sulfur vapor was seeded into a microwave-powered argon discharge and condensed at 12 K. Infrared spectra revealed sharp strong bands at 680.0, 676.2, 661.6, and 642.4 cm{sup {minus}1}, which were also observed by thermal dissociation of S{sub 8} flowing in a quartz tube heated to 400-900{degree}C. Increasing the sulfur concentration in the discharge favored the latter two relative to the former two absorptions. Enriched {sup 34}S samples gave isotopic shifts for pure sulfur fundamentals and isotopic multiplets that identify these species. Sample annealing produced a strong S{sub 2} chemiluminescence and a sharp new 674.5-cm{sup {minus}1} band. This feature revealed a sharp 1/2/1/1/2/1 sextet with 50/50 {sup 32}S/{sup 34}S, which confirms the observation of C{sub 2v} thiozone; similar multiplets were found for the 680.0- and 676.2-cm{sup {minus}1} bands. Calculations from four pairs of symmetrical isotopic v{sub 3} values gave 116 {plus minus} 2{degree} for the valence angle.

Infrared spectra of uranium hexafluoride, tungsten hexafluoride, molybdenum hexafluoride, and sulfur hexafluoride complexes with hydrogen fluoride in solid argon

Abstract: UF{sub 6}, WF{sub 6}, MoF{sub 6}, and SF{sub 6} have been codeposited with hydrogen fluoride in excess argon at 12 K. The FTIR spectra of UF{sub 6} and HF revealed a strong UF{sub 6}-HF complex absorption at 3,848 cm{sup {minus}1} along with a weak, broad band at 3,903 cm{sup {minus}1} due to the UF{sub 6}-FH complex. Only one 1:2 complex with a UF{sub 6}-H{sub a}F-H{sub b}F arrangement was detected at higher HF concentrations and sample annealings. Similarly, the HF interaction with tungsten hexafluoride formed two 1:1 complexes. However, the 3,884-cm{sup {minus}1} band due to the anti-hydrogen-bonded complex WF{sub 6}-FH was considerably stronger than the WF{sub 6}-FH{sub b}-FH{sub a} structure. The band positions and relative intensities for the MoF{sub 6} complexes with HF and DF were very comparable to their WF{sub 6} counterparts.

Matrix infrared spectra of hydrogen chloride complexes with uranium hexafluoride, tungsten hexafluoride and molybdenum hexafluoride

Abstract: HCl complexes with UF[sub 6], WF[sub 6], and MoF[sub 6] were prepared in solid argon at 12 K. The FTIR spectrum of UF[sub 6]/HCl contained a doublet at 2850.6 and 2849.7 cm[sup [minus]1] due to the hydrogen-bonded UF[sub 6]-HCl complex. In contrast, the HCl interaction with WF[sub 6], as well as MoF[sub 6] produced two distinctly different 1:1 complexes. The 2862.1-cm[sup [minus]1] absorption due to the antihydrogen-bonded complex, WF[sub 6]-ClH, was slightly more intense than the 2866.2 cm[sup [minus]1] absorption due to the antihydrogen-bonded complex, WF[sub 6]-ClH, was slightly more intense than the 2866.2-cm[sup [minus]1] absorption of the hydrogen-bonded complex, WF[sub 6]-HCl. The frequencies and relative intensities of the absorptions for the MoF[sub 6] complexes with HCl were very similar to those of their WF[sub 6] counterparts.

Matrix infrared and Raman spectra of the inequivalent submolecules in the ammonia dimer

Abstract: Vibrational modes in the N-H stretching region have been assigned to each submolecule in (NH 3 ) 2 on the basis of comparison of infrared and Raman spectra and the spectra of (NH 3 )(N(CH 3 ) 3 ) dimers. The submolecules are clearly different with one perturbed more strongly than the other and one exhibiting stronger Fermi resonance interaction between its internal ν 1 and 2ν 4 modes. The small vibrational perturbations show that the interaction is weaker than that normally associated with classical hydrogen bonding

Infrared and Optical Absorption Spectroscopy of Molecular Ions in Solid Argon

Abstract: The matrix isolation technique is particularly well-suited for the study of reactive species, including free radicals, molecular ions and molecular complexes, which react rapidly or decompose under normal chemical conditions. Matrix studies provide a valuable complement to gas phase work: band positions located in the matrix provide a guide for high resolution measurements and more information can often be obtained from a complete low resolution spectrum than from high resolution measurements on one band system.

Matrix-Infrared Spectra of Structural Isomers of the Phosphorus Oxysulfide P4S3O.

Abstract: Photolysis of the P 4 S 3 --O 3 molecular complex in solid argon with red light produced two sets of new infrared absorptions including terminal PO and symmetric P-S-P stretching modes, which are assigned to structural isomers of P 4 S 3 O with terminal oxygen at the apex and base phosphorus positions of P 4 S 3 . Further ultraviolet photolysis produced evidence for oxo-bridged P 4 S 3 O and a secondary product, P 4 S 3 O 2