The analysis of a 2 A 1 - 2 B 1 electronic band system of the AsH 2 and AsD 2 radicals

Abstract

Two new band systems have been observed in absorption following flash photolysis of AsH$_3$ and AsD$_3$, and are assigned to $^2$A$_1$-$^2$B$_1$ electronic transitions of AsH$_2$ and AsD$_2$. The origins of both systems are at 19 905 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 AsH$_2$ spectrum, leading to the following molecular parameters: ground state, r$''_0$ = 1.518 $\overset{\circ}{A}$ valence angle = 90$^\circ$ 44'; excited state, r'$_0$ = 1.48 $\overset{\circ}{A}$, valence angle = 123$^\circ$ 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).