High Resolution FTIR Study of PF 3 in the 800-950 cm -1 Region. The nu 1 and nu 3 Fundamental and nu 2 + nu 4 Combination Bands

Author： Sari-Zizi N.B. Burger H. Litz M. Najib H. Radtke J.

Publisher： Academic Press

ISSN： 0022-2852

Source： Journal of Molecular Spectroscopy, Vol.177, Iss.1, 1996-05, pp. : 46-57

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Abstract

The FTIR spectrum of PF 3 has been recorded in the 750-950 cm -1 range covering the fundamentals nu 1 (891.940 5 cm -1 ) and nu 3 (859.544 1 cm -1 ) and the combination band nu 2 + nu 4 (834.055 7 cm -1 ) with a resolution of ca. 2.5 x 10 -3 cm -1 . Furthermore, spectra of the 2nu 2 , 2nu 2 - nu 2 , (nu 2 + nu 4 ) - nu 4 , and (nu 2 + nu 4 ) - nu 2 bands were measured and analyzed. The vibrotational analysis of the nu 1 and nu 3 bands confirmed the presence of a Coriolis x , y resonance whose interaction parameter could be determined experimentally. A transition moment ratio mu 1 :mu 3 close to 0.7 has been deduced from a band contour simulation for a negative sign of the intensity perturbation mu 1 zeta 1,3 mu 3 . Furthermore, anharmonic resonance between nu 3 and nu 2 + nu 4 was established, the strength of which is in agreement with an interaction constant W 234 = 2.86 cm -1 as suggested by ab initio calculations. More than 5000 rovibrational transitions belonging to nu 1 , nu 3 , and nu 2 + nu 4 were fitted together with all available pure rotational data, sigma(Fit) of the IR data being 3.93 x 10 -4 cm -1 . It was found that q resonance within nu 3 induces an avoided crossing of the k $ell$ = 1, A - with the k $ell$ = -2, A - sublevel near J = 12. Its effects give rise to an irregular A 1 A 2 splitting of P ( PQR ) 3 lines and the R Q 0 branch near the crossing. The equilibrium rotational constants B e and C e have been determined, and their significance is critically assessed. An equilibrium structure, d e (PF) = 1.560 99(14) A and $angle$ FPF 97.57(4)#°, has been calculated.