Rotation Vibration Bands of Some Symmetric Top Molecules Under High Resolution

Abstract

The fine structure of some parallel bands of the symmetric top molecules CH3I, CD3Br, CHF3, and CHCl3 has been investigated in the 1.6 and 2.2μ regions. The double-pass plane grating spectrograph was capable of achieving a resolving power in excess of 100 000. For most of these bands the ``line'' nature of the sub-bands in the P, Q, and R branches was demonstrated. In the case of CH3I the resolution was complete enough to demonstrate conclusively the complicated fine structure of the P and R ``lines.'' Molecular constants have been derived from the bands of CH3I, CD3Br, and CHF3. The theoretically expected relationship between the zeta's has been shown to hold in perpendicular CH3I bands.