Mid-infrared laser absorption spectroscopy of the Ne-NO(X2Π) complex

The rovibrational spectrum of the Ne-NO(X-2 Pi) open-shell complex has been measured in the 5.3 mu m region using distributed feed-back quantum cascade lasers to probe the direct absorption in a slit-jet supersonic expansion. Three P-subbands (P ' <- P '': 1/2 <- 1/2, 3/2 <- 1/2, and 5/2 <- 3/2) were observed, where P is the projection of the angular momentum J along the inertial a-axis of the complex. The hyperfine structure due to the nuclei spin of N-14 (I = 1) was partially resolved in the P ' <- P '': 1/2 <- 1/2 and 3/2 <- 1/2 subbands. The observed mid-infrared spectrum of Ne-NO (X-2 Pi) together with the previously reported microwave spectrum was analyzed using a modified semirigid asymmetric rotor Hamiltonian for a planar open-shell complex. The band origin is located at 1876.0606(97) cm(-1), which is blue-shifted from that of the NO monomer by only 0.0888 cm(-1). The complex shows strong structural relaxation upon excitation of the overall rotation and the internal rotation of the NO subunit.