FAR-INFRARED LASER STARK SPECTROSCOPY OF METHANOL ISOTOPOMERS

Abstract

The Stark spectra of several methanol isotopomers ($CH_{3}OD, ^{13}CD_{3}OH, CD_{3}OH$, and $CD_{3}OD$) have been investigated in the far-infrared region using the HCN and DCN lasers. The spectra were recorded at room temperature for both parallel and perpendicular polarizations using electric fields up to 60 000 V/cm. Numerous transitions have been observed with these laser lines for all isotopomers. The following transitions will be presented: for $CH_{3}OD, I_{K}=6_{1}\leftarrow 5_{3}F_{2} \nu_{t}=0, J_{k}=18_{1}\leftarrow 18_{0} E_{2} \nu_{t} =1, J_{K} \ 14_{G} \leftarrow 13_{5}A \nu_{t} = 1;$ for $^{13}CD_{3}OH,J_{k}=18_{2}\leftarrow 17_{1}A^{-}\nu_{1}=0$; and for $CD_{3}OH,J_{K}=14_{1}\leftarrow 15_{0}E_{2} \nu_{1}=1$. Analysis of the recently recorded FTFIR spectra for $CD_{3}OD$ has yielded accurate zero-field frequencies belonging to the Q-branch multiplet for $K = 11 \leftarrow 10 E_{2}\nu_{t}=0$. By combining these results with the previously reported Stark fields for the $J = 11$ through 19 members, we have determined the electric dipole moment of this important molecular species for the first time.