Laser photoacoustic spectroscopy of iodine molecule: single and two-photon absorption

Abstract

Photoacoustic spectroscopy of iodine molecule has been studied in gas phase using nitrogen laser-pumped tunable dye laser. The experiment yielded the vibrational spectrum corresponding to X ¹∑ ⁺(0 _g ⁺ )→ B ³∏ (0 _g ⁺ ) transition up to the convergence limit. The photo-acoustic spectrum in the region 17580-18850 cm⁻¹ is presented along with the vibrational analysis. Five of the vibrational bands reported earlier by Venkateswarlu, Kumar and McGlynn have been partially resolved and the structure of one of them has been analyzed and shown to be due to an overlap of (14, 2) and (12, 1) bands. The analysis was based on a comparison with the highly resolved spectrum of Gerstenkorn and Luc. The structure observed in the region 20200-20750 cm⁻¹ which is beyond the convergence limit of the transition X ¹∑⁺(0 _g ⁺ )→ B ³∏(0 _u ⁺ ) has been analyzed as due to two-photon absorption. Most of the bands could be assigned to two transitions both originating in the ground state and terminating in two different electronic states 1 _g andE(0 _g ⁺ ), at T _e=40821 cm⁻¹ (or T ₀=41355 cm⁻¹) and T _e=41411 cm⁻¹ (or T ₀=41355 cm⁻¹) respectively.