Laser optogalvanic (LOG) and emission spectra of the N₂ molecule have been recorded at different discharge voltages and gas pressures in the spectral region 5400–6150 Å. It is observed that in the optogalvanic spectrum bands belonging to several systems develop extensively. Under the present discharge conditions bands of the first positive system are predominant. The variation of the signals with pressure and voltage in the two cases is discussed.

Two photon laser optogalvanic spectrum of theD-X system of HgBr molecule has been recorded using Nd-YAG laser pumped dye laser for the first time. A large number of new bands involving higher vibrational levels have been observed. Isotopic heads due to the two bromine isotopes have been observed and used in fixing the vibrational assignment. Vibrational constants for theX andD states of the two isotopic molecules have been determined.

The vibrational overtone spectra of aryl and alkyl C-H stretch vibrations in benzaldehyde have been studied using conventional IR and thermal lensing technique at room temperature. The stretching vibrational frequencyω_e, anharmonicity constantω_ex_e and the dissociation energies of the two C-H bonds have been calculated. The bond length of C-H bond in aryl position has been estimated.