The analysis of a 2 A 1-2 B 1 electronic band system of the AsH2 and AsD2 radicals

Two new band systems have been observed in absorption following flash photolysis of AsH3 and AsD3, and are assigned to 2A1 - 2B1 electronic transitions of AsH2 and AsD2. The origins of both systems are at 19905 cm-1. The bands have the complex rotational structure associated with an asymmetric rotor. Rotational analyses have been carried out for three bands of the AsH2 spectrum, leading to the following molecular parameters: ground state, r"0 = 1.518 Å valence angle = 90° 44'; excited state, r'0 = 1.48 Å, valence angle = 123° 0'. The parameters associated with rotation about the a inertial axis increase rapidly with increase in v'2. The spectrum shows doublet splittings of up to 41 cm-1, and the excited state furnishes the first example of a doublet state of an asymmetric top molecule which shows substantial departures from Hund’s case (b).