Accurate Wavenumber Measurement in High Resolution Stimulated Raman Spectroscopy (SRS) by Using an Infrared Standard. ν₁ Fundamental of ¹²CH₄

Abstract

A new set of wavenumbers for the Stimulated Raman Spectrum (SRS) of the ν1 band of 12CH4 is presented using the Infrared (IR) absorption spectrum of the P10 component of ν3 of the same molecule as a wavenumbers standard. An estimation of the Stark shift due to the pump laser field is experimentally deduced what allows to extrapolate the measured wavenumbers to zero field amplitude. A careful discussion about the main possible error sources and how to cope with them is also included.The absolute accuracy of the wavenumbers set presented here is believed to be at least one order of magnitude better as compared with previous measurement.

Linewidths of C2H2 perturbed by H2: experiments and calculations from an ab initio potential

“…The accuracy of the surface is tested by a quantum determination of pressure broadening coefficients which are compared with current experimental measurements of isotropic Raman lines of the acetylene ν 2 band at 143 K. The experimental technique used for this purpose is stimulated Raman loss spectroscopy [1,44]. Such experimental data are the first ones 3 reported for the title collisional system.…”

Inverse R aman Spectrometry

“…Higher peak power may result in a degradation of the resolving power because of the magnetic sublevel splitting due to the ACStark effect. 15,25,26 As the strength of the SRS signal does not depend on the degree of focusing, long focal length lenses (¾500 mm) are used (unless a good spatial resolution is required) in order to decrease the power density in the focal region and, therefore, the above mentioned AC-Stark broadening.…”

“…between 150 MHz intervals. 25 For the wavenumber calibration two main different approaches are possible. One possibility is to measure the wavenumber of the CW dye laser at the beginning and at the end of every scan with a high accuracy wavemeter.…”

“…In 1992, Santos et al 85 reported spectra of this molecule at 77 K and room temperature. 85 In order to improve the accuracy of the wavenumber determination, the pump and probe lasers were mixed in a LiNbO 3 crystal to generate the IR frequency difference radiation.…”

“…85 In order to improve the accuracy of the wavenumber determination, the pump and probe lasers were mixed in a LiNbO 3 crystal to generate the IR frequency difference radiation. This radiation was used to record, simultaneously with the SRS spectrum, an IR absorption spectrum of some lines of n 3 lying in the same spectral region that were used as a standard for calibration.…”