An analysis of the spectrum of the linear unsymmetric molecule HC12N has been made permitting the determination of the 21 constants necessary for predicting the vibrational frequencies and the 10 constants necessary for predicting the B value for the various vibrational states. To determine these constants new measurements were made on numerous bands in the region of 1–3 μ employing a 5-m vacuum spectrograph. Several instances of Fermi resonance were detected and analyzed. Except for a few bands where additional resonances may be present, the vibrational constants predict the measured values for the band origins of 44 bands within an amount not much greater than the expected experimental error. The rotational constants also predict the B value within the experimental error for 24 bands where data are available.
Bands of HC13N and DC12N were also measured to determine the α values for calculation of the equilibrium moment of inertia. The 101–000 and 1111–0110 bands were used for all three isotopic forms of HCN to determine the Be values in a parallel fashion. From these values the bond length C–H=1.06593±0.00010 A and C–N=1.15313±0.00002 A were determined.
In five different cases in HC12N it was possible to apply the Ritz combination principle to determine the frequency of the 0110 state. By using this value and the rotational constants it was possible to calculate the frequencies of lines in the 0110–000 band. The principle is also applied to HC13N and DC12N.
© 1960 Optical Society of AmericaFull Article | PDF Article
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