Thomas C. James

Infrared Spectra of Gaseous Transition‐Metal Dihalides

The infrared spectra of gaseous MnCl2, FeCl2, CoCl2, NiCl2, CuCl2, and CoBr2 have been measured in absorption between 220 and 4000 cm—1. With the exceptions of MnCl2 and CuCl2, the emission spectra of these molecules have also been obtained in this region. The emission from unsaturated vapor indicates that one of the two absorptions observed for each of the dihalides, other than manganous chloride, is attributable to a vibration of a polymeric species. Assuming that the monomeric dihalide molecules have D∞h symmetry, the monomeric absorption is assigned to ν3, the antisymmetric stretching vibration. The M—X bond stretching force constants calculated using the linear model and a simple valence force field are quite similar to those of the corresponding diatomic monohalides. Both sets of constants show a maximum between manganese and zinc.

Line Intensities in the Raman Effect of 1Σ Diatomic Molecules

The effect of rotation‐vibration interaction on line intensities in the Raman effect is examined. Both the rotation‐vibration and pure rotation spectra are discussed. It is shown that from a study of relative line intensities one can obtain the quantities β0/β1re and κ12/β12, where β0 and β1 are the first two terms in the expansion of the anisotropy of the polarizability about the equilibrium internuclear distance re, and κ1 is the derivative with respect to internuclear distance of the spherical part of the polarizability. The treatment considers only the case of a harmonic oscillator and is carried through to terms of order γ2, where γ = 2Be/ωe.

Intensity Measurements in the B3Π0u+ − X 1Σ0+g System of I2

Equivalent width measurements were made on rotational lines in six vibrational bands in the B–X system of I2. All measurements were made photoelectrically. Calculations of the Doppler, natural, and collisional widths show the Doppler width to be 340 times larger than the combined natural and collisional width at 22°C. Measurement of the equivalent width at several path lengths for each line confirmed a pure Doppler curve of growth for the lines. From known spectroscopic data the line strengths gave a value for the square of the electronic contribution to the transition moment, and for the value of the total Einstein spontaneous emission rate from each υ′ to all υ″ with nonzero Franck–Condon factors. A comparison of these purely radiative decay rates with total decay rates measured by Chutjian, Link, and Brewer and by Davis and Grimes shows the presence of a significant amount of spontaneous predissociation of the B state to ground‐state 2P3/2 iodine atoms. In the absence of collisions approximately 66% of...

Infrared Spectrum and Dipole Moment Function of Lithium Hydride

Line intensities in the 0–1 and 1–2 rotation‐vibration bands of lithium hydride at 7 μ have been measured. The ratio of the dipole moment to the dipole derivative is ue/(∂u/∂r)re re=1.8±0.3. It is shown that the dipole moment of a diatomic molecule approaches the united atom limit as the third power of the internuclear separation.

Rotation‐Vibration Interaction in Electronic Transitions. Application to Rotational ``Temperature'' Measurements

The effect of rotation‐vibration interaction on line intensities in electronic transitions in diatomic molecules is discussed. It is shown that this effect is closely related to the variation in the electronic transition moment with internuclear distance. The relation of this to the determination of rotational temperatures is discussed, using the OH radical as an example. It is shown that a neglect of this interaction can lead to the observation of apparently abnormal temperatures.