Knowledge Bank

We obtain Doppler resolution limited $(\Delta \nu \simeq 0.0020cm-1)$ spectra of the P and R multiplets for J $\le 10$ of the $10\mu mC-O$ stretch band $(\nu 4)$ of $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}CD316OH$ using a tunable diode laser. These multiplets are composed of 3J and 3J+3 lines for the P and R multiplets, respectively, the individual lines being associated with the hindered rotation and K substructure. The inta-multiplet spreading is $\simeq 0.1cm-1$, in contrast to $CH3OH$, where the spreading is $\sim 1.0cm-1$. We are able to resolve most of the substructure and assign the transitions in the low-J multiplets. The assignments are based primarily on the results of Stark-difference spectra, combined with the microwave ground state $data1$ and the intensities expected theoretically. The A, K=0 and $A\pm$, K=1 lines, due to their negligible Stark effects, can be readily assigned from high’’ field spectra $(\sim 2\times 10^{3} \mbox{v/cm})$. The Stark components of the remaining lines are so severely overlapped at high fields, however, that the systematics in the low’’ field $(\sim 400v/cm)$ Stark difference spectra are most useful in making their assignments. From combination relations we find the ground and excited state $A\pm$, K=1 asymmetry splitting parameters to be $\delta 1\prime =(8.5450\pm 0.0080)\times 10-3cm-1$ and $\delta 1\prime =(9.7706\pm 0.0080)\times 10-3cm-1$, respectively, where the energy separation of the asymmetry split levels varies as $\delta J(J+1)$. The data are recorded digitally using a rapid-scan, double-beam system and the spectra are plotted on a linearized wave-number axis with the aid of a computer. Relative frequency is determined from the co-recorded channel spectrum of a germanium etalon to a precision of $\pm 3\times 10-4cm-1$, while absolute frequency accurate to $\pm 1\times 10-3cm-1$ is obtained from FTIR spectra calibrated against the 10 $\mu mCO2$ laser lines measured in absorption.