MEASUREMENTS OF ARGON COLLISION BROADENING IN THE CN B-2-SIGMA(+)[-X(2)SIGMA(+)(0,0) SPECTRUM

Absorption line shapes in the (0,0) band of the B <-- X violet system of CN are measured in shock tube experiments using a rapid-tuning narrow-line ring dye laser. Excimer photolysis at 193 nm and high temperature pyrolysis of C2N2-Ar mixtures are used for CN generation. In experiments using the shock tube as a room temperature (298 K) cell, the rotational quantum number (N '') dependence of the CN-Ar collision broadening coefficient is determined by modeling the recorded line shapes with Voigt profiles. Transitions in the P-branch with lower state rotational quantum numbers of N '' = 4-14 are probed; the expression 2 gamma(CN-Ar)(tau=298) (K) [cm(-1) atm(-1)] = 0.0560 exp(-0.201 N '') + 0.11 results. Shock tube experiments over the temperature range 1200-4500 K are used to determine the temperature dependence of the collision broadening coefficient, resulting in the expression 2 gamma(CN-Ar)[cm(-1) = atm(-1)] 2 gamma (tau=298K)(CN-Ar)(298/T)[K])(0.8) valid for temperatures from 298 to 4500 K. r= 298 K Additional measurements confirm the magnitude of the (0,0) band oscillator strength and validate the spectral absorption coefficients calculated with a spectroscopic model of the CN B <-- X (0,0) system for a wide range of conditions.