Microwave and millimeter wave study o Ortho-N_2 states of CO-N_2

摘要

Microwave and millimeter wave transitions of the CO-N_2 complex were investigated using three different instruments, namely, a pulsed molecular beam Fourier transform microwave spectrometer in the frequency region from 4 to 26 GHz, a microwave-millimeter wave double resonance spectrometer in the frequency regions from 8 to 18 GHz for the microwave and 107-118 GHz for the millimeter wave range, and an OROTRON spectrometer in the frequency range from 107 to 132 GHz. Both a- and b-type transitions associated with the ground-state K = 0 levels and the lower K = 1 levels of the ortho-N_2 states, and with rotational quantum number J up to 19, were measured and analyzed. Nuclear quadrupole hyperfine splittings due to the presence of two equivalent ~(14)N nuclei were resolved and analyzed to give additional information about the angular anisotropy of the interaction potential. The nuclear quadrupole coupling constants obtained are #chi#_(aa) = 0.196 41(52) MHz for K = 0 levels, and #chi#_(aa) = -1.0391(17)MHz, #chi#_(bb) = 0.0633(17)MHz for the lower K = 1 levels, respectively. The drastic difference between these two sets of coupling constants suggests that the orientation and motion of the N_2 subunit are very different in these two states, and that the complex cannot be adequately described by a semirigid rotor model. In addition, measurements of the rotational spectra of the two new isotopomers containing ~(13)C~(16)O and ~(13)C~(18)O subunits provide further important information about the CO-N_2 interaction potential.