Abstract
All six infrared active fundamental bands of cyclopropane-D 6 were studied at high resolution (âź0.2 cm â1) and vibrational and rotational constants derived. Of the parallel fundamentals, ν 6 was reanalyzed with much greater precision than in a previous study, and an analysis of ν 7 was performed. Two of the four perpendicular fundamentals exhibit analyzable rotational structure â ν 9, which has a clearly defined Q branch structure, and ν 10, which has the appearance of a parallel band, and analyzes as such within the limits of the rigid rotor approximation. Accordingly, the value of Îś 10 is estimated to lie within Âą0.015 of the value of ( 1 â BⲠCⲠ) required to give a zero subband spacing in a perpendicular band. Of the remaining two perpendicular fundamentals, ν 8 is not resolved but exhibits a well defined PQR contour; ν 11 closely resembles a parallel band, the J structure of which exhibits definite in- and out-of-phase characteristics, but which does not analyze satisfactorily in terms of parallel band equations. These bands were analyzed by computer simulation. For ν 8, an approximate value for Îś 8 is obtained only, and no information on the rotational constants Îą 8 C and Îą 8 B . For ν 11, only one set of the variables Îś 11, Îą 11 C , Îą 11 B was found which reproduces the observed contour essentially perfectly. For the perpendicular bands, the theoretical Îś sum rule is well obeyed. Two of the perpendicular bands exhibit â-type resonance perturbations around their band centers. The possible effects of ignoring such perturbations on the precision of the results are discussed.
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