Study of collisional relaxation of acetylene with spherical photoacoustic cell

摘要

With a spherical cell, photoacoustic resonance experiments have been performed for C_2H_2. The first radial mode of the spherical cell was excited using the chopped beam of a Ti: sapphire laser. High Q value of 590 has been achieved for C_2H_2 gas at the pressure of 50 Torr. The resonant peak broadening is mainly due to the vibrational-translational relaxation of C_2H_2. An expression for acoustic amplitude as a function of modulation frequency, relaxation time, and other parameters has been derived. This theoretical formula was fitted to the experimental data, and the relaxation time was then determined. Our work reveals a double relaxation process for C_2H_2.