Pressure broadening by argon in the hyperfine resolved P(10) and P(70) (17,1) transitions of I2 X1Σ(0g+)→B3Π(0u+) using sub-Doppler laser saturation spectroscopy

The dependence of pressure broadening upon hyperfine component in the P(10) and P(70) lines of the (17,1) band of the I2 X1Σ(0g+)→B3Π(0u+) has been studied using laser saturation spectroscopy. By limiting absorption to the zero velocity group, Doppler broadening is removed, lineshapes with widths (FWHM) <9 MHz are detectable, and collision-induced broadening is measured at pressures of 0.2-1.2 Torr. The rates for broadening by argon are 8.3±0.3 and 10.7±0.4 MHz/Torr for the P(70) and P(10) lines, respectively. No significant variation in broadening rates is observed for the 15 hyperfine components of these even rotational lines. The effects of velocity cross-relaxation introduce a broad baseline into the spectra, which is strongly dependent on rotational state, pressure, and laser modulation frequency. The observed broadening rates correlate well with prior measurements and the polarizability of the collision partner.