Inversion vibration of P H 3 + ( X ̃ A 2 ″ 2 ) studied by zero kinetic energy photoelectron spectroscopy

We report the first rotationally resolved spectroscopic studies on P H 3 + ( X ̃ A 2 ″ 2 ) using zero kinetic energy photoelectron spectroscopy and coherent VUV radiation. The spectra about 8000 cm − 1 above the ground vibrational state of P H 3 + ( X ̃ A 2 ″ 2 ) have been recorded. We observed the vibrational energy level splittings of P H 3 + ( X ̃ A 2 ″ 2 ) due to the tunneling effect in the inversion (symmetric bending) vibration ( ν 2 + ) . The energy splitting for the first inversion vibrational state ( 0 + ∕ 0 − ) is 5.8 cm − 1 . The inversion vibrational energy levels, rotational constants, and adiabatic ionization energies (IEs) for ν 2 + = 0 - 16 have been determined. The bond angles between the neighboring P-H bonds and the P-H bond lengths are also obtained using the experimentally determined rotational constants. With the increasing of the inversion vibrational excitations ( ν 2 + ) , the bond lengths (P-H) increase a little and the bond angles (H-P-H) decrease a lot. The inversion vibrational energy levels have also been calculated by using one dimensional potential model and the results are in good agreement with the experimental data for the first several vibrational levels. In addition to inversion vibration, we also observed firstly the other two vibrational modes: the symmetric P-H stretching vibration ( ν 1 + ) and the degenerate bending vibration ( ν 4 + ) . The fundamental frequencies for ν 1 + and ν 4 + are 2461.6 ( ± 2 ) and 1043.9 ( ± 2 ) cm − 1 , respectively. The first IE for P H 3 was determined as 79670.9 ( ± 1 ) cm − 1 .