Emission Spectroscopy and Ab Initio Calculations on IrN

Abstract

The emission spectrum of IrN was recorded in the near infrared using a Fourier transform spectrometer. The IrN molecules were excited in an Ir hollow cathode lamp operated with a mixture of Ne and a trace of N2. Numerous IrN bands observed in the 7500–9200 cm−1 region were assigned to a new a3Π–X1Σ+ electronic transition with the 0–0 bands of the a3Π0–X1Σ+ and a3Π1–X1Σ+ subbands near 9175 and 8841 cm−1, respectively. A rotational analysis of several bands of the 0–0 and 0–1 sequences was obtained and molecular constants were extracted. The effective Hund's case (a) constants for the new a3Π state are: T00 = 8840.31747(88) cm−1, A0 = −340.53329(93) cm−1, ΔG(1/2) = 984.3629(23) cm−1, Be = 0.4699116(27) cm−1, αe = 0.0030058(50) cm−1, and re= 1.6576432(47) Å. The spectroscopic properties of the ground state and several low-lying electronic states of IrN were also predicted by ab initio calculations. These calculations are consistent with our assignment of the a3Π–X1Σ+ transition and also support our previous assignments of the A′ 1Π and A1Π electronic states [R. S. Ram and P. F. Bernath, J. Mol. Spectrosc. 193, 363 (1999)]. The excited a3Π state of IrN has an 1ς22ς21π43ς11δ42π1 electron configuration and the configurations of the other low-lying electronic states are also discussed.