Showing papers by "Willis B. Person published in 1978"

Analysis of 3ν3 in SF6

Abstract: Studies of the 3ν3 absorption band in SF6 in the spectral region from 2800 to 2850 cm−1 have been completed with a FT–IR spectrometer at a spectral resolution of 0.04 cm−1. This study confirms the results reported earlier by Kildal on the general shape of this absorption band. The absorption has been studied as a function of temperature, allowing a definite assignment to be made of the ground state features observed in this spectrum at room temperature. The ground state absorption to 3ν3 appears with a double Q branch [estimated band origins at 2830.22 and 2827.62 (±0.06) cm−1]. The intensities and temperature dependence studies confirm the assignment by Fox of these two Q branches to the two F1u components of the 3ν3 state.

Dipole moment derivatives and infrared intensities. IV. Prediction of absolute infrared intensities of the fundamental vibrations of CF2 and CF3 radicals

Abstract: Absolute infrared intensities have been predicted for the fundamental absorption bands of CF2 and CF3 radicals, using an F atomic polar tensor transferred from CH3F. The predicted relative intensities have been compared with the experimental spectra of the matrix‐isolated radicals with satisfying results. The effect on the predictions resulting from modification of the transferred polar tensor is examined by using F atom polar tensors from CF2H2 and from CNDO/2 and INDO calculations. The scatter of the predicted values suggests that the predictions of the absolute integrated molar absorption coefficients may be expected to be accurate within a range of about ±30%, and so would be of potential use in semiquantitative analytical applications.

Measurements of some line positions and strengths in the ν4 region of SF6

Abstract: Absolute ’’line strength’’ measurements with a diode laser spectrometer are reported for a number of J‐manifolds for ν4 of SF6 in the gas phase. These results are analyzed to obtain the ν4 vibrational band strength: S0V≡A= (83±11 km mole−1. A critical discussion is presented of errors in line and band strength measurements in general, and of these results in particular. The experimental procedure was calibrated by measurements on several rotational lines in ν2 of N2O; the vibrational band strength derived for that transition in N2O is S0V=A=7.71±0.76 km mole−1, in excellent agreement with the literature value from total integrated band area measurements. The measured value for S0V for ν4 of SF6 is compared with literature values, and the discrepancy is discussed.

Absolute integrated intensities of the infrared absorption bands of TiCl4

Abstract: The absolute integrated molar absorption coefficients Ai have been measured for the ν3 fundamental and for the stronger binary combination bands of TiCl4 in the vapor phase. The experimental value for A3, the coefficient of the TiCl4 ν3 fundamental vibration, is 277±42 km mole−1. This value is compared with 320 ±40 km mole−1 predicted from the mean transition movement ‖μz01‖?0.29±0.04 D given by Fox and Person for asymmetric X–Cl stretching vibrations of tetrahedral molecules. Another prediction, based on transfer of effective charges for the Cl atom, yields A3≲125 km mole−1. The implications of these results are discussed.

Determination of the Concentrations of CF2 and CF3 Radicals in an Argon Matrix: An Illustration Using Predicted Infrared Intensities

Abstract: A novel procedure is described for the determination of concentrations of CF2 and CF3 radicals from the infrared spectrum using predicted values for the absolute integrated molar absorption coefficients. The predictions were made using an F-atom polar tensor transferred from CH3F according to procedures described earlier. These predicted intensities are used to calculate a simulated spectrum, adjusting the values assumed for the concentrations of CF4, CF3, and CF2 until agreement is obtained with the experimental spectrum obtained by Milligan and Jacox from a sample of CF2N2 photolyzed in an argon matrix in the presence of an added F-atom source. This procedure illustrates an analytical application of predicted infrared intensities that may also be important for other unstable species.