Low-temperature absorption spectrum of the (0120)-(0000) <sup>13</sup>CH<sub>4</sub> band. Line assignment
The 13CH4 absorption spectra in the range between 7400 and 7600 cm-1 have been recorded at for temperatures from 296 to 200 K by the Fourier spectrometer IFS-125M at a spectral resolution of 0.03 cm-1. A 220 cm cell was used, which provided a threshold sensitivity to absorption on the order of 10-6 cm-1. Line assignment of the n2 + 2n3 band of the 13CH4 molecule was performed. Rotational constants of the (0120) state and the integral intensity of the n2 + 2n313CH4 band were determined for the first time.