Gas-phase water: Features of hydrogen bonding deduced from far-infrared VRT spectra proving the cluster formation in vacuum

Far-infrared vibration-rotation-tunneling (VRT) spectra of gas-phase water reported previously have been interpreted in terms of polaronic exciton coupled model. An increase of the energy gap (Delta nu) between the neighboring absorption lines, which is observed in the spectrum within a pattern responsible for water cluster absorption, correlates with spin-orbit coupling parameter (beta). Namely, experimental ratio (Delta nu(i+1)/Delta nu(i)) = 1.188996 +/- 0.051361 has been found in fair agreement with beta = 1.19100654 that implies the accumulation of difference between the absorption and emission energies. This correlation means the electrons coupled with protons establishing hydrogen bonds accumulate the energy difference. Relation deduced earlier for Boson peak frequency admitted to estimate fast Debye relaxation time for water that is found to be 0.183704 ps.