Recent Line-Shape And Doppler Thermometry Studies Involving Transitions In The Ν₁ +Ν₃ Band Of Acetylene
Creators: name: Hashemi, Robab
name: Rozario, Hoimonti
name: Povey, Chad
name: Garber, Jolene
name: Derksen, Mark
name: Predoi-Cross, Adriana
Publisher: name: Zenodo
Year: 2014
Subjects: Poster Session

description: The line positions for transitions in the <em>ν</em><sub>1 </sub>+<em>ν</em><sub>3 </sub>band are often used as a frequency standard by the telecom industry and also needed for planetary atmospheric studies. Four relevant studies have been recently carried out in our group and will be discussed briefly below. (1) <em>N</em><sub>2</sub>-broadened line widths and <em>N</em><sub>2</sub>-pressure induced line shifts have been measured for transitions in the <em>ν</em><sub>1 </sub>+<em>ν</em><sub>3 </sub>band of acetylene at seven temperatures in the range 213333K to obtain the temperature dependences of broadening and shift coefficients. The Voigt and hard-collision line profile models were used to retrieve the line parameters. This study has been published in Molecular Physics, 110 Issue 21/22 (2012) 2645-2663. (2) Six nitrogen perturbed transitions of acetylene within the <em>ν</em><sub>1 </sub>+<em>ν</em><sub>3 </sub>absorption band have been recorded using a 3-channel diode laser spectrometer. We have examined <em>C</em><sub>2</sub><em>H</em><sub>2 </sub>spectra using a hard collision (Rautian) profile over a range of five temperatures (213 K-333 K). From these fits we have obtained the <em>N</em><sub>2</sub>-broadening and narrowing coefficients of <em>C</em><sub>2</sub><em>H</em><sub>2 </sub>and examined their temperature dependence. The experimentally measured narrowing coefficients have been used to estimate the nitrogen diffusion coefficients. The broadening coefficients and corresponding temperature dependence exponents have also been compared to that of calculations completed using a classical impact approach on an ab initio potential energy surface. We have observed a good agreement between our theoretical and experimental results. This study was published in Canadian Journal of Physics 91(11) 896-905 (2013). (3) An extension of the previous study was to analyze the room temperature for the same six transitions using the Voigt, Rautian, Galatry, RautianGalatry and Correlated Rautian profiles. For the entire pressure range, we have tested the applicability of these line-shape models. Except for Voigt profile, Dicke narrowing effect has been considered in all mentioned line-shape models. The experimental results for the narrowing parameters have been compared with calculated values based on the theory of diffusion. This study is in press in press in the Journal of Quantitative Spectroscopy and Radiative Transfer. (4) In this paper we present accurate measurements of the fundamental Boltzmann constant based on a lineshape analysis of acetylene spectra in the <em>ν</em><sub>1 </sub>+<em>ν</em><sub>3 </sub>band recorded using a tunable diode laser. Experimental spectra recorded at low pressures have been analyzed using both the Voigt model and the Speed Dependent Voigt model that takes into account the molecular speed dependence effects. These line-shape models reproduces the experimental data with high accuracy and allow us to determine precise line-shape parameters for the transitions used, the Doppler-width and then determined the Boltzmann constant, <em>k</em><em><sub>B</sub></em>. This study has been submitted for publication in the Journal of Chemical Physics. <sup>1</sup>

 

 

1 Research described in this work was funded by NSERC, Canada.
description: Poster Session II: June 24, 2014.