Self‐broadening and line mixing in HCN Q branches

摘要: Q‐branch spectra of the ν1+ν2 (4004 cm−1) and ν2+ν3 (2806 combination bands ν1−ν2 (2599 difference hot band HCN have been recorded at pressures from 0.13 to 53.3 kPa (1 400 Torr) using a tunable difference‐frequency laser. The self‐broadening coefficients are same for all three involving ν2 Π bending mode within experimental error those reported previously other Σ vibrational bands. J dependence exhibits maximum near peak Boltzmann population distribution, is well described by semiclassical line‐broadening theory incorporating known measured or ab initio dipole quadrupole moments polarizabilities, classical trajectories an isotropic Lennard‐Jones short‐range potential. Line mixing evident in strongly overlapped, higher pressure profiles nonadditive Lorentzian superposition component transitions. However, line coupling moderated f→...