STUDY OF THE UPSILON(4)=2 AND UPSILON(4)=3 STATES OF PF3 BY HIGH-RESOLUTION INFRARED-SPECTROSCOPY

In order to study the upsilon(4) = 2 and upsilon(4) = 3 states of PF3, two high resolution (approximate to 3 x 10(-3) cm(-1)) infrared spect ra were used. In the 14 mu m region, 2 nu(4)(0) and the hot band 3 nu( 4)(+/-1) - nu(4)(+/-1) could be analysed but the 2 nu(4)(+/-2) and 3 n u(4)(+/-3) - nu(4)(+/-1) bands were not observed. Amen:: the hot bands of nu(4) at 28 mu m, however, the hot bands 2 nu(4)(+/-2) - nu(4)(+/- 1) and 3 nu(4)(+/-3) - 2 nu(4)(+/-2) could not be identified. Altogeth er 1166 transitions of 2 nu(4)(0) and 198 energy levels deduced from 2 nu(4)(+/-2) - nu(4)(+/-1) were fitted to a model taking into account the l(2,2) interaction between the upsilon(4) = 2(0) and upsilon(4) = 2(+/-2) states. Five microwave transitions were also included in the f it. A standard deviation of 0.241 x 10(-3) cm(-1) was obtained. A simi lar model for upsilon(4) = 3 implying l(2,2) interaction terms between upsilon(4) = 3(+/-1) and 3(+/-3) as well as between 3(+1) and 3(-1) w as used to fit 491 energy levels of upsilon(4) = 3(+/-1) and 97 of ups ilon(4) = 3(+/-3). These were deduced from hot bands; six microwave tr ansitions were also included in the fit, which gave a standard deviati on sigma = 1.201 x 10(-3) cm(-1). The anharmonic constants deduced fro m the experimental bandcenters (2 nu(4)(0))(0) = 692.84694(3) cm(-1) a nd (3 nu(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 (2 nu(4)(+/-2 ))(0) = 694.695 cm(-1) and (3 nu(4)(+/-3))(0) = 1042.633 cm(-1) are in fair agreement with the predictions from nu(4) and the above-mentione d anharmonic constants. (C) 1997 Academic Press.