Microwave spectrum of the ClO radical

Abstract

The rotational transitions J = 3 2 ← 1 2 in the 2 Π 1 2 state of the free radicals 35ClO and 37ClO have been observed with a Stark-modulated microwave spectrometer. The ClO radical is detected as a reaction intermediate in the discharge products of a mixture of chlorine and oxygen. The molecular constants such as the rotational constant, the Λ-type doubling constant and the hyper-fine constants are determined accurately. The reasonable assumption that the sign of d = 3g NμNβ〈 sin 2 χ r 3 〉 is positive leads to the determination of the symmetry of each Λ-type doublet level, and it is concluded that the upper electronic state which causes the Λ-type doubling is 2Σ +, located approximately 31000 cm −1 above the ground 2Π state. The equilibrium internuclear distance is determined to be r e = 1.569 ± 0.004 A ̊ by the use of the rotational constants of 35ClO and 37ClO. The average concentration of the ClO radical in the absorption cell is estimated to be about 0.5%.