The v(4)=1 and v(4)=2 rovibrational levels of PF3 revisited: New solutions for old topics

摘要

The high-resolution infrared spectra of trifluorophosphine (PF3) were reinvestigated in the v(4) fundamental region near 350 cm(-1), and around 690 cm(-1), with the aim to provide a necessary reassignment of the 2(+/- 2) sublevel of the v(4) = 2 overtone level. The present paper reports on the first complete study of both sublevels of v(4) = 2 (of A(1) and E symmetry, corresponding to 14 = 0 and +/- 2, respectively), through the high-resolution analysis of the overtone 2v(4)(0), band and the 2v(4)(+/- 2) - v(4)(+/- 1) hot band. The assignments of the latter were corrected and extended, spanning the rotational states J <= 82 and -80 <= K" . Delta k <= 48. These new infrared assignments in the v(4) = 2 state were combined with accurate infrared, radiofrequency, centimeter-, millimeter- and submillimeter-wave data of the v(4) = 1 level (Thiessen et al., 2000), together with rotational data in the ground vibrational state (Cotti et al., 1995), in a simultaneous fit. The existence of resonance crossings due to a Delta k = +/- 1, Delta l = -/+ 2 l-type resonance in the v(4) = 1 state, which generated perturbation-allowed transitions, provided independent values of the C-4 and C zeta(4) constants. Combining these rotational transitions with the wavenumbers of the v(4) fundamental band enabled us to determine accurately the C-0 axial ground state constant. Moreover, the assignment of a few, very weak R-r(K) transitions in the 2v(4)(-2) overtone band and their inclusion in the global least-squares fit allowed also the first accurate experimental determination of D-k(0). The obtained results are (in cm(-1)): C-0 = 0.159970241(29) and D-k(0)=1.80457(49) x 10(-7).