Temperature-dependent pressure broadened line shape measurements in the ν1+ν3 band of acetylene using a diode laser referenced to a frequency comb

• Published in: Applied physics. B, Lasers and optics Vol. 109; no. 3; pp. 373 - 384
• Main Authors: Cich, M. J., McRaven, C. P., Lopez, G. V., Sears, T. J., Hurtmans, D., Mantz, A. W.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 2012
• Subjects: Engineering; Lasers; Optical Devices; Optics; Photonics; Physical Chemistry; Physics; Physics and Astronomy; Quantum Optics; Pressure Shift; Line Shape; Line Shape Function; Optical Frequency Comb; Frequency Comb
• ISSN: 0946-2171; 1432-0649
• DOI: 10.1007/s00340-011-4829-0

Using an extended cavity diode laser referenced to a femtosecond frequency comb, the P(11) absorption line in the
ν
1
+
ν
3
combination band of the most abundant isotopologue of pure acetylene was studied at temperatures of 296, 240, 200, 175, 165, 160, 155, and 150 K to determine pressure-dependent line shape parameters at these temperatures. The laser emission profile, the instrumental resolution, is a Lorentz function characterized by a half width at half the maximum emission (HWHM) of 8.3×10
−6
 cm
−1
(or 250 kHz) for these measurements. Six collision models were tested in fitting the experimental data: Voigt, speed-dependent Voigt, Rautian–Sobel’man, Galatry, and two Rautian–Galatry hybrid models (with and without speed-dependence). Only the speed-dependent Voigt model was able to fit the data to the experimental noise level at all temperatures and for pressures between 3 and nearly 360 torr. The variations of the speed-dependent Voigt profile line shape parameters with temperature were also characterized, and this model accurately reproduces the observations over their entire range of temperature and pressure.