MICROWAVE, SUBMILLIMETER-WAVE, AND HIGH-RESOLUTION FTIR SPECTRA OF ASF3 IN THE NU(2) AND NU(4) STATES

The nu(2) (nu(0) = 337.796 4 cm(-1)) and nu(4) bands (nu(0) = 262.994 2 cm(-1)) of AsF3 have been studied by FTIR spectroscopy with a resolu tion of ca. 3 x 10(-3) cm(-1). Several hot bands of nu(2) were identif ied and analyzed. Rotational transitions with J = 0 <-- 1 and 1 <-- 2 in the upsilon(2) = 1 excited state and Delta J = 0, l-type resonance transitions within the nu(4) excited state have been measured for 10 l ess than or equal to J less than or equal to 38 and 0 less than or equ al to G = \k - l\ less than or equal to 6 in the 4.5-26.5 GHz region b y FT microwave techniques. Furthermore, millimeter-wave transitions be longing to the upsilon(2) = 1 and 2 and upsilon(4) = 1 excited states have been studied in the 340-470 GHz region. All available rotational and rovibrational data related to the nu(2), 2 nu(2), and nu(4) states were appropriately weighted, merged, and fitted, and numerous excited state parameters were determined. While the vl and 2 nu(2) states are unperturbed, the nu(4) state is strongly affected by Delta G = 0, 3, and 6 interactions. The concept of unitary equivalent reduction of the effective Hamiltonian (H. Harder, C. Gerke, H. Mader, J. Cosleou, R. Bocquet, J. Demaison, D. Papousek, and K. Sarka, J. Mol. Spectrosc. 16 7, 24-41 (1994)) has been applied, the validity of this concept for th e nu(4) State of AsF3 has been proved by the precise and numerous pres ent data, and some formerly observed empirical relations between the f itted parameters have been shown to be fulfilled. By means of the accu rate rotational constant, C-0 = 0.137 799 2(5) cm(-1), an improved r(0 ) structure of AsF3 was obtained, r(0)(AsF) = 1.708 58 Angstrom and al pha(0)(FAsF) = 96.055 degrees. (C) 1996 Academic Press, Inc.