Tunable diode laser measurements of spectral parameters of HCN at room temperature

A tunable infrared diode laser was used to record 17 fully resolved vibration-rotation transitions in the v₁ fundamental band of HCN at 3μ. The experiments were conducted in an absorption cell on room temperature mixtures of HCN diluted by N₂ and Ar. The v₁ fundamental band strength of HCN was determined to be 267±8 cm^-2 atm^-1 at 273.2 K. Small but significant reductions in the residual errors were obtained by using the Galatry profile rather than the Voigt profile to fit the experimentally recorded line shapes. Collisional broadening and narrowing parameters were determined simultaneously from Galatry profile fits to the data. The collision-broadened linewidths of HCN lines in N₂ and Ar were determined as a function of rotational quantum number of transitions ranging from P(14) to R(14) (3268.22-3353.29 cm^-1). The optical diffusion coefficients of HCN in N₂ and Ar at 300 K were determined from the collisional narrowing parameters and were 0.074±0.01 and 0.016±0.03 cm²s^-1 respectively.