Molecular Dynamics Simulation of Vibrational Phase Relaxation along the Critical Isochore of Nitrogen : The Role of Local Density Fluctuations

Swapan Roychowdhury; Biman Bagchi

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Molecular Dynamics Simulation of Vibrational Phase Relaxation along the Critical Isochore of Nitrogen : The Role of Local Density Fluctuations

Swapan Roychowdhury·Biman Bagchi

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Abstract

Vibrational dephasing of nitrogen molecule is known to show highly interesting anomalies near its gas-liquid critical point. Here we present theoretical and computational studies of the Raman linewidth of nitrogen along the critical isochore. The linewidth is found to have a lambda shaped temperature dependence near the critical point. As observed in experimental studies, the calculated lineshape becomes Gaussian as the critical temperature ($T_{c}$) is approached. Both the present simulation and a mode coupling theory (MCT) analysis show that the slow decay of the enhanced density fluctuations near the critical point (CP), probed at the sub-picosecond time scales by vibrational frequency modulation, along with an enhanced vibration-rotation coupling, are the main causes of the observed anomalies.

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Swapan Roychowdhury, Biman Bagchi. 2003-01-24. Molecular Dynamics Simulation of Vibrational Phase Relaxation along the Critical Isochore of Nitrogen : The Role of Local Density Fluctuations. https://arxiv.org/abs/physics/0210039

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