Interference effects in the high Resolution CARS spectra of gases

✍ Scribed by J. Laane; W. Kiefer

• Publisher: John Wiley and Sons
• Year: 1980
• Tongue: English
• Weight: 556 KB
• Volume: 9
• Category: Article
• ISSN: 0377-0486
• DOI: 10.1002/jrs.1250090603

✦ Synopsis

Abstract

The CARS spectra of gas‐phase molecules have contributions from both real and imaginary components of the third‐order non‐linear susceptibility. When the spectral lines are closely spaced as in the high‐resolution CARS spectra (e.g. ˜ 0.03 cm^−1^) of the Q‐branches of diatomic molecules, considerable interference between the lines occurs for the contribution of the real part of the susceptibility, which causes asymmetry in the band profiles. The magnitude of the interference is dependent on the bandwidths Γ which are themselves primarily due to pressure broadening at high and medium pressures and due to Doppler broadening at low pressure. In this work the CARS spectra of two individual lines and of the diatomic molecules O~2~, N~2~ and NO have been calculated for a number of different linewidths. The effects of interference wereshown to result in substantial spectral differences for the various values of Γ.