MICROWAVE SPECTRUM OF METHYL DIFLUOROPHOSPHATE

The microwave spectrum of methyl diflurophosphate, $CH_{3}OP(O)F_{2}$, was investigated in the region of 26,500 to 40,000 MHz employing Stark modulation and radiofrequency microwave double resonance (RFMDR) techniques, and in the region of 6000 to 18000 MHz by means of a pulsed beam Fourier transform spectrometer. Under fast scan, low resolution conditions, two $u_{a}$-type prolate rotor band series were observed with B+C values of 4955.5(5) MHz and 4973.4(10) MHz. $u_{a}$- and $u_{b}$-type transitions arising from the 4955.5 band series were found with the pulsed beam spectrometer. However, extensive searches with the Fourier transform system did not reveal the presence of the $\\mu_{a}$-type $J=2 + 1$ and $J=3 \\leftarrow 2$ lines from the 4973.4 MHz B+C species. A centrifugal distortion analysis of the $u_{a}$- and $u_{b}$-type transitions obtained in both spectral regions yields the rotational constants (MHz): $$A = 4568.215(8) B = 2500.728(2) C = 2453.847(2)$$ Efforts to assign the second series by Stark and RFMDR techniques and possible conformational assignments will be discussed.