Symmetry Reduction and Rotational Re-quantization of Symmetric Top Molecules at Local Mode Limit

The (400) stretching overtone band of AsH₃ has been observed near 8029.0 cm^-1 and analyzed in both symmetric and asymmetric top models. The results indicate that the dynamical symmetry of the (400) local mode state has reduced to that of an asymmetric top and the rotational energy levels can be assigned by a set of quantum numbers J, K_a, and K_c.