Infrared spectra and tunneling dynamics of the N_2-D_2O and OC-D_2O complexes in the v 2 bend region of D_2O

摘要

The rovibrational spectra of the N_2-D_2O and OC-D_2O complexes in the v2 bend region of D_2O have been measured in a supersonic slit jet expansion using a rapid-scan tunable diode laser spectrometer. Both a-type and b-type transitions were observed for these two complexes. All transitions are doubled, due to the heavy water tunneling within the complexes. Assuming the tunneling splittings are the same in K_a = 0 and K_a = 1, the band origins, all three rotational and several distortion constants of each tunneling state were determined for N_2-D_2O in the ground and excited vibrational states, and for OC-D_2O in the excited vibrational state, respectively. The averaged band origin of OC-D_2O is blueshifted by 2.241 cm-1 from that of the v2 band of the D_2O monomer, compared with 1.247 cm~(-1) for N_2-D_2O. The tunneling splitting of N_2-D_2O in the ground state is 0.16359(28) cm~(-1), which is about five times that of OC-D_2O. The tunneling splittings decrease by about 26% for N_2-D_2O and 23% for OC-D_2O, respectively, upon excitation of the D_2O bending vibration, indicating an increase of the tunneling barrier in the excited vibrational state. The tunneling splittings are found to have a strong dependence on intramolecular vibrational excitation as well as a weak dependence on quantum number K_a.