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Argon-Induced Pressure Broadening, Shifting, and Narrowing in the CN A2Π–X2Σ+ (1–0) Band

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journal contribution
posted on 21.11.2013 by Damien Forthomme, Christopher P. McRaven, Trevor J. Sears, Gregory E. Hall
Selected isolated rotational transitions in the 1–0 band of the red A2Π–X 2Σ+ system in CN have been recorded with transient frequency modulation spectroscopy as a function of argon pressure up to 0.2 atm at room temperature. Line shapes were fit using Fourier transforms of a parametrized time correlation function, including Doppler and velocity-dependent collisional broadening, and collisional shifts. Deviations from Voigt line shapes can be equally well fit by modeling the narrowing with a speed-dependent collision model or with a velocity-changing collisional narrowing model. Pressure broadening coefficients were observed with little rotational state dependence, in the range of 0.070–0.075 cm–1 atm–1. In contrast, stronger and qualitatively different rotational state dependences are observed for both pressure-dependent blue shift coefficients and the narrowing parameters. No asymmetry in the pressure broadened lines was observed.