Larned B. Asprey

Vibrational Spectra and Force Constants for Isotopic Species of Nitrosyl Chloride

From infrared absorption studies in the gaseous phase, fundamental harmonic vibrational frequencies have been determined for 16O14N35Cl, 16O15N35Cl, 18O14N35Cl, and 18O15N35Cl. With the aid of centrifugal‐distortion data from the literature, a unique general quadratic valence‐force‐constant solution was obtained. The resulting values are: FNO = 15.26 mdyn A−1, FNCl = 1.27 mdyn A−1, Fα = 1.32 mdyn A−1·rad−2, FNO,NCl = 1.53 mdyn A−1, FNO,α = 0.1 mdyn rad−1, FNCl,α = 0.12 mdyn rad−1.

Electronic and vibronic states of uranium hexafluoride in the gas and in the solid phase at very low temperatures

Complex vibronic structure has been observed in the electric‐dipole‐forbidden charge transfer absorption bands of solid and matrix‐isolated UF6 in the temperature range 8–14 K. These bands have their maximum intensity near 260 and 375 nm. Associated with the 260 nm band are four electronic transitions with origins at 30 331, 31 032, 32 120, and 32 821 cm−1, the first two being observed directly. Two more no‐phonon transitions are associated with the weak band at 375 nm, one at 24 564 cm−1 and another at 25 265 cm−1. These levels are assigned via a weak j‐j coupling scheme as excitations from the ligand t1uσ orbital to empty uranium 5f orbitals. Uranium spin–orbit coupling in UF6 charge transfer states strongly resembles that of UF6 −. Several progressions in the symmetric stretch frequency ν1=580–595 cm−1 are present which have as their origins various combinations of the above electronic levels with the bending modes ν4, ν5, and ν6 or their overtones 2ν4, 2ν5, and 2ν6. Temperature effects, which account ...

Vibrational Spectra and Force Constants for Nitrosyl Fluoride and 15N and 18O Species

From infrared absorption studies in the gaseous phase, the fundamental harmonic vibrational frequencies have been determined for 16O14NF, 16O15NF, 18O14NF, and 18O15NF. Two quite different force constant solutions were obtained in a general quadratic valence force field. With the aid of centrifugal distortion constants and the inertial defect, it was possible to select the true force constant solution: FNO=15.9 mdyn A−1; FNF=2.3 mdyn A−1; Fα=1.8 mdyn·Arad−2; FNO,NF=2.5 mdyn A−1; FNO,α=0.27 mdyn rad−1; FNF,α=0.20 mdyn rad−1. These force constants were converted to those of a modified Urey—Bradley force field and a general quadratic central force field. It is shown that the latter gives unreasonable force constants. Interaction displacement coordinates were calculated and correlated qualitatively with valence‐bond theory.

The electronic spectrum of cesium hexafluoromanganese(IV)

Abstract A number of high purity samples of Cs 2 MnF 6 have been prepared and their electronic spectra studied, both in absorption and emission. The observed peaks were assigned to the crystalfield energy levels for an octahedral d 3 configuration. A large number of vibronic components have been observed and correlated with data on the ground state vibrational frequencies. Evidence of spin-orbit splitting of several of the bands was adduced. Recent work on the MnF 6 2− complex was examined and some of the discrepancies discussed. The crystal-field parameters have been derived, and a value for the optical electronegativity of Mn(IV) calculated. The results are: D q = 2180 cm −1 , B = 650 cm −1 , C = 3972 cm −1 , and χ opt = 2.90. The nephelauxetic ratios are β 55 = β 35 = 0.61.

Vibrational spectroscopy of matrix‐isolated UF6 and UF5

The vibrational spectrum of UF6 molecules isolated in Ar, Xe, and CO matrices is reported. Also, the ir spectrum of monomeric UF5 molecules produced in these matrices by photolysics with uv radiation is reported. (AIP)

Experimental and calculated electronic structure of gaseous CrO2F2 and CrO2Cl2

The gas phase electronic absorption spectra of CrO2F2 and CrO2Cl2 have been measured in the visible, near ultraviolet regions. Interpretation has been made by comparison with a molecular orbital calculation for each molecule by the SCF‐Xα‐SW method. The calculated ground and excited states and observed electronic transitions correlate directly with those for the parent isoelectronic CrO2−4 and MnO−4 species.

Coriolis constants of spherical-top molecules from low-temperature infrared studies of vapor band contours: Application to the force field of tungsten hexafluoride☆

Abstract The infrared-active stretching fundamental ν 3 of WF 6 vapor has been studied over the temperature range T = 190–310 K. At lower temperatures the hot-band structure is sufficiently suppressed to allow accurate measurements of the P-R branch spacing, which is a linear function of T 1 2 . From the slope of a least-squares line fitting 36 measured spacings, the Coriolis constant is found to be ζ 3 = 0.123. Enough overtone and combination bands have been observed in the infrared and laser Raman spectra of WF 6 for harmonic fundamental frequencies to be estimated. Harmonic force constants are calculated, using ζ 3 as the necessary additional constraint in the F 1 u symmetry block. Possible sources of error are discussed and error limits are estimated for all reported frequencies and force constants. The valence stretching force constant is r = 5.50 ± 0.07 mdyn/ A .

Vibrational Spectrum and Force Field of Ruthenium Tetroxide

Infrared and Raman spectra are reported for the vapor and liquid phases of Ru16O4 and Ru18O4. Anharmonicity corrections were estimated for the observed isotope shifts, and Coriolis constants were obtained from the infrared band contours. General quadratic force constants are calculated, using as constraints the 16O–18O and 96Ru–102Ru isotope shifts, Coriolis constants, and vibrational amplitudes; the relative effectiveness of these and the effects of the anharmonicity corrections are discussed. The force field is nearly extremal. The valence stretching force constant is fr = 6.99±0.04 mdyn/A, appreciably less than for OsO4. Standard‐state thermodynamic functions for RuO4 vapor are calculated for the temperature range 273–500°K.

Vibrational spectra and force constants for isotopic species of nitrosyl bromide

Abstract From infrared absorption studies in the gaseous phase, the fundamental harmonic vibrational frequencies have been determined for 16 O 14 NBr, 16 O 15 NBr, 18 O 14 NBr, and 18 O 15 NBr. With the aid of centrifugal distortion data from the literature, a unique general quadratic valence force constant solution was obtained. The resulting values are: F NO = 15.25 md/A, F NBr = 1.13 md/A, F α = 1.13 md A/rad 2 , F NO,NBr = 1.47 md/A, F NO, α = 0.11 md/rad, and F NBr, α = 0.10 md/rad. Interaction displacement coordinates were calculated and were used along with the force constants to describe the bonding in ONBr, ONCl, and ONF.

Chemistry of trifluoromethyl compounds : I. NMR evidence for bis(trifluoromethyl)zinc and methyl(trifluoromethyl)zinc

Abstract Bis(trifluoromethyl)zinc and methyl(trifluoromethyl)zinc have been identified by 19 F and 1H NMR methods. The compounds were formed in the following reactions: (1) dimethylzinc and bis(trifluoromethyl)mercury and (2) dimethylzinc and bis(trifluoromethyl)cadmium.