The spectroscopy of MnH

The low-lying quintet and septet states of MnH have been studied using the state-averaged CASSCF MRCI method. Our study focuses on the A⁷Π-X⁷Σ⁺, c⁵Σ⁺-a⁵Σ⁺, and b⁵Π-a⁵Σ⁺ band systems, which almost certainly correspond to the 566-, 847-, and 939-nm band systems observed in emission. The radiative lifetimes for the v′ = 0 level of the A⁷Π, b⁵Π, and c⁵Σ⁺ states are 96.6 ns and 3.2 and 0.39 μs, respectively. Although the CASSCF calculations are not inconsistent with the assignment of the 480-nm band system to a ⁵Π-a⁵Σ⁺ transition, they indicate the existence of a stronger ⁵Σ⁺-a⁵Σ⁺ transition in the same energy region. The calculations also show that the quintet spectrum above 20 000 cm^-1 is very complicated.