Knowledge Bank

The $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}CD3OH$ methanol isotopomer is known to be an efficient FIR lasing molecule when optically pumped by a $CO2$ laser. Over 200 FIR laser lines have been detected in the laboratory to date and about 80 have been frequency measured. These include the third most efficient known FIR laser line at $127\mu$m and a very long wavelength line at 2615 $\mu$m. The IR spectrum of $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}CD3OH$ in the 9 and $10\mu$ m regions is very rich. Several fundamentals have been recorded at high resolution and spectroscopically analyzed, including the in-plane $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}CD3$-rocking, $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}$CO-stretch and $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}CD3$-deformation bands. The IR spectra are complex due to level crossings and torsion-rotation-vibration interactions, reducing confidence in the IR assignment. However, we have benefited greatly in the past from clear confirmation of some of our results as a by-product of assignments of a variety of IR-pump/FIR-laser transition systems. Observations of FIR laser lines give direct, first-hand information about transitions in the excited vibrational state which in difficult to obtain by other means. This work extends our identifications of IR-pump/FJR-laser line systems. The $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}CD3OH$IR spectrum was revisited and several new systems have been spectroscopically assigned. Of particular note are high- K systems for which the FIR laser excited-state information provided sufficient clues to identify the corresponding weak IR subbands in the spectrum. Most of the new assignments have been rigorously checked by forming closed combination loops with known high resolution data to confirm the FIR laser assignments in some cases and to give predictions of unknown FIR laser lines nr improved wavenumbers in other cases. In the course of this work, we have critically reviewed and updated all known information on the IR-pump FIR-laser observations and spectroscopic assignments for $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}CD3OH$, resulting in significant corrections to the existing literature on assignments. Detailed assignments along with energy schemes will be presented.