Identification and analysis of the perturbed c 3Pi(v=1)-X 1Sigma+ and k 3Pi(v=5)-X 1Sigma+ absorption bands of carbon monoxide

International audienceTwo new red-degraded bands in the room-temperature vacuum-ultraviolet absorption spectrum of carbon monoxide have been identified in the 94 000-94 500 cm-1 energy region and analyzed. One of the bands at ~94 225 cm-1 (106.1 nm) has three observable bandheads and is partially overlapped with the strong C 1Sigma+-X 1Sigma+ (1-0) transition at lower energy. It is assigned to the c 3Pi-X 1Sigma+ (1-0) transition. The other band at ~94 437 cm-1 (105.9 nm) with one clear bandhead is assigned to the k 3Pi-X 1Sigma+ (5-0) transition. A strong homogeneous perturbation was found to exist between the two upper states that strongly influences the line positions and shapes of these bands. A rotational deperturbation analysis was performed and molecular rotational constants for both upper states were determined. These deperturbed molecular constants are entirely consistent with the expected values for the k 3Pi valence and c 3Pi Rydberg states. The Hamiltonian interaction term between these two states is found to be separable into vibrational and electronic factors and the electronic factor is determined to be He=323+/-40 cm-1. A discrepancy in the literature regarding the location of the c 3Pi (v=1) state is identified and discussed