Spectrum of NBr Excited in Active Nitrogen

Abstract

The spectrum of NBr near 6000 A, excited by the action of active nitrogen on bromine, has been photographed at high dispersion and the rotational structure of the bands has been analyzed. The bands have been attributed to a ${}^1{\Sigma }^{+}{-}^3{\Sigma }^{-}$ transition in which the ³Σ^— state is the ground state of the molecule. Only two of the five possible branches were observed, both of them belonging to the F₁(J=N+1) component of the ³Σ^— state. The unusual structure of the bands is attributed to the fact that the coupling in the ³Σ^— state is intermediate between Hund's case b and case c. The equilibrium internuclear distances are r_e′=1.731 A and r_e″=1.79±0.02 A and the dissociation energy is estimated to be 67±5 kcal. The emission spectrum is believed to be caused by the combination of N(⁴S) and $\mathrm{Br}{(}^2{P}_{\frac{3}{2}})$ atoms into some unknown excited state of NBr which is induced, by wall collisions, into the ¹Σ⁺ state.