Interpretation and analysis of perturbed spectra of axially symmetric molecules with applications to 13CD3F

The main thrust of this study is the development and testing of an algorithm to fit perturbed vibration-rotation molecular spectra. The algorithm is first developed in a general form and then applied to the vibration-rotation spectra of axially symmetric molecules using simulated data. The 5 μm absortion spectrum of 13CD3F is very complex. There are 24 vibrational levels in the region form 1800 cm-1 to 2250 cm-1. There are many strong vibrational and rotational resonances linking these states. The states included in this analysis are ν4(l4 = +/-1), 2ν2(l = 0), ν2 + ν5(l5 = +/-1), 2ν5(l5 = 0,+/-2), ν2 + ν3(l = 0),ν1(l = 0) and ν3 + ν5(l5 = +/-1), all of which lie above 2050 cm-1. The states omitted in this analysis are ν2 + ν6(l6 = +/-1), ν5 + ν6(l5 = +/-1,ν6 = +/-1), 2ν3(l = 0), ν3 + ν6(l6 = +/-1), and 2ν6(l6 = 0,+/-2), all of which lie below 2050 cm-1. These two groups of vibrational states are weakly linked by a higher order vibration-rotation resonance between ν1 and ν6(l6 = -1) and weak vibrational resonance between ν1 and 2ν3. The absorption spectrum of 13CD3F was recorded at a resolution of 0.018 cm-1 and deconvolved to an effective resolution of 0.006 cm-1. The ν1, 2ν5(l5 = 0), 2ν2 and ν4(l4 = +/-1) bands were analyzed individually to obtain estimates of the molecular parameters of these states. The local and nonlocal resonances were characterized and interaction constants were estimated, which gave a qualitative agreement with the observed spectrum. The parameters were then refined using a Hamiltonian model which included all possible interactions from the vibration-rotation Hamiltonian through third order with the restriction that ΔK -ΣKAPPA/ =0