Optical–optical double resonance (OODR) studies of the ion-pair states of the halogens. Part 1.—Vibronic threshold for the chemiluminescent reaction between I2(ƒ 0 +g) and Xe

Abstract

The technique of optical–optical double-resonance (OODR) spectroscopy has been used to study the collisional dynamics of the ƒ(0⁺_g) state of I₂ in the presence of Xe. Using the B(³Π_0⁺u) state as an intermediate we have succeeded in selectively populating specific rovibronic levels of the ƒ(0⁺_g) state from v′= 0 up to v′= 107. Dispersed fluorescence has been observed from a number of single rovibronic levels in this range. The energetic threshold for the chemiluminescent reaction I₂(ƒ 0⁺_g, v′=n)+ Xe → XeI(B²Σ_1/2)+ I(²P_3/2) has been determined as 52 460 ± 400 cm^–1, which corresponds to v′= 52–57. The reaction was monitored by observing fluorescence from XeI(B²Σ_1/2) at 253 nm.