We have studied thengr;3fundamental of fluoroform at 700 cmminus;1with a resolution of 0.3 cmminus;1, obtaining a contour showing a series of wellhyphen;resolvedPandRbranch ldquo;lines.rdquo; A rotational analysis is performed which determines the groundhyphen; and first excited vibrational state rotational and distortion constants. A computer program for the calculation of symmetrichyphen;top parallel band contours is critically tested by comparison of the experimental and calculated envelopes of thengr;3HCF3band. Thengr;4band of phosphorous pentafluoride at 575 cmminus;1is studied with a resolution of 0.5 cmminus;1giving an unresolved but wellhyphen;defined contour which is analyzed by comparison with calculated contours. The results give Psngbnd;F axial bond lengththinsp;equals;thinsp;1.581 Aring;, Psngbnd;F equatorial bond lengththinsp;equals;thinsp;1.534 Aring; in the ground vibrational state. Thengr;6fundamental of cyclopropane is examined under a resolution of 0.3 cmminus;1, giving a wellhyphen;resolved series ofPandRbranch ldquo;lines.rdquo; TheB0value for cyclohyphen;C3H6found from this band is 0.6688 cmminus;1, whileC0thinsp;equals;thinsp;0.420cmminus;1.
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