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column 3) or the phase correction of ref 3 (column 4). It is evident that the phase correction expression of ref 3 is valid for the case AV = 0, but not when AV 0.In conclusion, therefore, we have confirmed that use of the type of WKB edge-effect correction originally proposed by Le Roy et al.3 can greatly accelerate the convergence of numerical tunneling probability calculations for potentials with long-range tails. However, for asymmetric barriers, the expression for the WKB phase correction given in ref 3 is in error and should be replaced by the present more general eq 8 and 9.

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The free radical HCCN was produced in an Ar matrix via photolysis of its precursor diazoacetonitrile, NNCHCN, with radiation of wavelengths longer than 350 nm. The ir spectra of HCCN and three isotopic modifications (DCCN, HC13CN, and HCC15N) were obtained, and normal coordinate analyses based on two different geometries, bent and linear, were carried out. The results provide a determination of the general valence force field, and favor the linear, allenic configuration H–Ċ=C=Ṅ. The electronic spectrum of HCCN in an argon matrix was also obtained. A tentative assignment of the band system observed in the uv part of the spectrum has been made.

The infrared absorption spectrum of carbon monoxide in an argon matrix shows prominent bands at 2148.8 and 2138.0 cm—1 with half-widths, respectively, 1.5 cm—1 and 3.5 cm—1. The relative intensities of these bands are extremely dependent upon a variety of experimental conditions, including sample concentration, window temperature, and deposition rates. The variability shows that CO isolated in argon absorbs at 2148.8 cm—1 and that it does not rotate. The lower frequency absorption is due to aggregates. The frequency shift of the argon-isolated CO absorption relative to that of gaseous CO shows that carbon monoxide fits tightly in the argon lattice. In contrast, the CO aggregates absorb at lower frequency than gaseous carbon monoxide. Isotopic studies using 13C16O reveal vibrational coupling of 1.1 cm—1 between isotopically identical molecules in an aggregate. An increase in matrix cavity diameter would be needed if a stationary CO molecule begins to rotate in argon. This ``site expansion,'' which could be as much as 0.4 Å, may be an important factor inhibiting rotation.

Raman scattering from crystalline NaNO3 has been observed in all polarization orientations. Except for small intensity contributions in some orientations which are probably due to depolarization effects in the birefringent crystal, the polarizability activities of both internal and external modes follow the expected symmetry selection rules. From relative intensity considerations, the bands at 185 and 98 cm− 1 have been designated as the Raman-active librational and translational lattice modes, respectively. This assignment has been confirmed by the comparison of the lattice spectra of Na14NO3 and Na15NO3 at 35°K, where an isotope shift is observed only on the lower frequency band. No evidence of mixing between these Eg lattice modes has been observed.