Subquadratic Quantum Number Dependence and Other Anomalies of Vibrational Dephasing in Liquid Nitrogen: Molecular Dynamics Simulation Study from the Triple Point to the Critical Point and Beyond

Vibrational phase relaxation near gas-liquid and liquid-solid phase coexistence has been studied by molecular dynamics simulations of N-N stretch in ${\mathrm{N}}_2$. Experimentally observed pronounced insensitivity of phase relaxation from the triple point to beyond the boiling point is found to originate from a competition between density relaxation and resonant-energy transfer terms. The sharp rise in relaxation rate near the critical point (CP) can be attributed at least partly to the sharp rise in vibration-rotation coupling contribution. Substantial subquadratic quantum number dependence of overtone dephasing rate is found near the CP and in supercritical fluids.