Fourier transform infrared and millimeter-wave study of the v2=1v2=1, 2 and the v2=v4=1v2=v4=1 rovibrational states of 14NF314NF3

The 2121 (A1A1; 647.13 cm-1cm-1), 2222 (A1A1; 1292.26cm-1) and 21412141 (E  ; 1138.28cm-1) excited states of 14NF314NF3 have been studied by high-resolution FTIR spectroscopy with a resolution between 2.3 and 3.0×10-3cm-1, and by millimeter-wave (MMW) spectroscopy. For the 2121 state, 3380 non-zero weighted (NZW) ν2ν2 infrared (IR) transitions (Jmax=Kmax=70Jmax=Kmax=70) and 59 MMW transitions (Jmax=27Jmax=27, Kmax=21Kmax=21) were fitted together, with respective rms deviations σIR=0.142×10-3cm-1 and σMMW=28σMMW=28 kHz, using an unperturbed model up to sextic centrifugal distortion constants. The lower state parameters were constrained to those of the ground state. Similarly we have fitted 2181 NZW transitions (Jmax=Kmax=60Jmax=Kmax=60) of the 2ν2-ν22ν2-ν2 hot band merged with 54 MMW transitions (Jmax=21Jmax=21, Kmax=13Kmax=13) measured in the 2222 state and employing the 2121 parameters for the lower state. Respective rms deviations were σIR=0.263×10-3cm-1 and σMMW=58σMMW=58 kHz. The anharmonicity constant x22=-1.00606(1)cm-1 was determined. The v2=2v2=2 state is better determined by the 2ν2-ν22ν2-ν2 rather than the obtained 2ν22ν2 IR data owing to the weakness of 2ν22ν2. To the contrary the strong and isolated ν2+ν4±1 combination band is much better suited to probe the 21412141 state than the ν2+ν4±1-ν4±1 hot band. Therefore 4375 NZW IR lines (Jmax=Kmax=69Jmax=Kmax=69) of ν2+ν4ν2+ν4 and 119 MMW transitions belonging to the 21412141 state with Jmax=Kmax=13Jmax=Kmax=13 were fitted together using the same model as for the ν4ν4 fundamental band. This model takes into account ll(2, 2), ll(2, −1), ll(2, −4), and (0, 6) intravibrational interactions when the D reduction of the Hamiltonian is employed. The corresponding rms of deviations were σIR=0.270×10-3cm-1 and σMMW=227σMMW=227 kHz; similar rms values were also obtained for Q and QD reductions refining uniformly 22 parameters. The anharmonicity constant x24=-2.27995(3)cm-1 was determined.