Study of Coupling mechanism of optical and acoustic energy in the Time Resolved Pulsed Photoacoustic spectrum of I2 molecules at Different Temperature and Pressure.
The paper reports the time resolved pulsed photoacoustic study of I2 molecules using a single 532 nm, pulses of 7 ns duration at 10 Hz repetition rate obtained from Q- switched Nd:YAG laser. Frank -Condon principle based assignments confirms the presence of several numbers of ( ν”- ν’) vibrational transitions covered by a single 532 + 2nm pulse profile. The strongest vibronic transition lines correspond to (32-0) and (31-0) transitions have the maximum intensities andpart of equally separated bandwidth of the laser pulse. These strongest acoustic modes of I2 molecules are located at 4000 Hz and 14650 Hz, respectively. The separation of frequency between these two strongest modes is of the order of 10650 Hz. The experiment was repeated with different sized PA cell and found once again that two strongest acoustic modes of I2 molecules occur at 10.75 KHz and 21.45 KHz frequency range are separated by 10650 Hz only.For the first time, our experimental findings confirm that the frequency of the excited modes are controlled by cavity dimension whereas separation between the two strongest cavity modes are governed by the laser pulse profile. Moreover, the pressure and temperature based study demonstrates the exchange energy mechanism between the excited acoustic modes inside the PA cavity.