Study of thev4= 2 andv4= 3 States of PF3by High Resolution Infrared Spectroscopy

Abstract In order to study the v 4 = 2 and v 4 = 3 states of PF 3 , two high resolution (≈3 × 10 −3 cm −1 ) infrared spectra were used. In the 14 μm region, 2ν 4 0 and the hot band 3ν 4 ±1 − ν 4 ±1 could be analysed but the 2ν 4 ±2 and 3ν 4 ±3 − ν 4 ±1 bands were not observed. Among the hot bands of ν 4 at 28 μm, however, the hot bands 2ν 4 ±2 − ν 4 ±1 and 3ν 4 ±3 − 2ν 4 ±2 could be identified. Altogether 1166 transitions of 2ν 4 0 and 198 energy levels deduced from 2ν 4 ±2 − ν 4 ±1 were fitted to a model taking into account the l (2,2) interaction between the v 4 = 2 0 and v 4 = 2 ±2 states. Five microwave transitions were also included in the fit. A standard deviation of 0.241 × 10 −3 cm −1 was obtained. A similar model for v 4 = 3 implying l (2,2) interaction terms between v 4 = 3 ±1 and 3 ±3 as well as between 3 +1 and 3 −1 was used to fit 491 energy levels of v 4 = 3 ±1 and 97 of v 4 = 3 ±3 . These were deduced from hot bands; six microwave transitions were also included in the fit, which gave a standard deviation σ = 1.201 × 10 −3 cm −1 . The anharmonic constants deduced from the experimental bandcenters (2ν 4 0 ) 0 = 692.84694(3) cm −1 and (3ν 4 ±1 ) 0 = 1039.0697(3) cm −1 are x 44 = −0.2154 cm −1 and g 44 = 0.4474 cm −1 . The experimental bandcenters (2ν 4 ±2 ) 0 = 694.695 cm −1 and (3ν 4 ±3 ) 0 = 1042.633 cm −1 are in fair agreement with the predictions from ν 4 and the above-mentioned anharmonic constants.