Knowledge Bank

Microwave (MW), millimieter-wave (MMW) and fourier-transform far-infrared (FTFIR) transitions in the first two torsional states ($vl=0$ below the barrier and $vl=1$ straddling the barrier) of the ground vibrational state of C-13 methanol have been globally treated and successfully fitted to within assigned measurement uncertainties using a program (1. Kleiner and M. Godefroid private communication) originally designed for acetaldehyde ($CH3CHO$) based on the formalism of Herbst et al. (J. Mol. Spectrosc. 108, 42-57, 1984). The $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}CH13OH$ data set ($vt\le 1.J\le 20,Kmax\le 14$) contains 725 MW and MMW lines, assigned a $\pm$50 kHz measurement uncertainty apart from a few $K$-doublet lines, and 6283 FTFIR lines each assigned an uncertainty of $\pm$$0.0002cm-1=\pm 6$ MHz. A very satisfactory convergent fit has been achieved using 55 adjustable and 2 fixed parameters, yielding an overall weighted standard deviation of 0.962. Calculations employing the parameters from our final fit reveal possible C - 13 assignments for 28 lines appearing in natural abundance in the newly-measured methanol microwave atlas from 7 to 200 GHz compiled by the group of K. Takagi at Toyama university. The present C - 13 work together with the previous global fitting for $CH3OH$ (J. Mol. Spectrosc. 169, 396-409, 1995 and 173, 540-551, 1995) set the groundwork for a critical review of the available MW and MMW spectra of $CH3OH$ and its most abundant isotopomer, $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}CH3OH$, for astrophysical application. This review includes frequency calculations based on our torsion-rotation analyses with line uncertainties estimated from the variance-covariance matrices, along with the original references for observed lines. The primary objective of the review is to provide radio astronomers with complete spectral coverage of rotational transitions from 500 MHz to 1 THz. Including the lower state energy and line strength for each transition, over the range in rotational quantum number $J$ from 0 to 26.