It is shown that use of a balanced detector based on common mode rejection improves the line shape of rovibrational transitions of water vapour considerably. The line shape can be fitted by using Voigt profile. The residuals can be reduced by using collisionally narrowed Galatry profile, but the Dicke narrowing conditions are not satisfied for water vapour in this region of spectroscopy. In such cases, the improvement of fit may become a mathematical artifice without any useful information. Ar-broadened line shape parameters of three water vapour transitions of the 2 1 1 overtone band in the 12 150 cm -1 region are presented. © 2004 Elsevier B.V. All rights reserved.

BISWAJIT RAY

Physics

A BANDYOPADHYAY

A RAY

P N GHOSH

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Chemical Physics Letters

The line shape parameters of water vapour rovibrational transition at 12145.444 cm-1 belonging to the (2ν1 + ν2 + ν3) overtone band in the presence of three buffer gases He, N2 and CO2 are studied by high resolution near infrared (NIR) diode laser spectrometer. The wavelength modulation spectroscopy (WMS) is adopted to probe buffer gas broadened first derivative (1f) signal of water vapour transition. The simulation of the experimental signals based on Voigt profile provides the collisional broadening coefficients and line strength parameters. The comparison is made between the broadening effects on water vapour transition induced by He, N2 and CO2. © 2010 Elsevier B.V. All rights reserved.

Vibrational Spectroscopy

A comparative study of the effects of different buffer gases on the line shape of water vapour rovibronic transition

We report the CO2-induced broadening coefficients and line strength parameters of water vapor rovibrational transitions belonging to the (2v(1) + v(2) + v(3)) overtone band measured by using an NIR diode laser spectrometer. Rotational quantum number dependence of the broadening coefficients is also shown. Use of balanced photodetector and wavelength modulation spectroscopy with small current modulation amplitude helped to obtain improved S/N ratio of the spectra. The recorded line shapes are fitted with standard Voigt profile by using a non-linear least squares fitting program to extract the line shape parameters. (C) 2008 Elsevier B.V. All rights reserved.

Measurement and analysis of rotational lines in the (2v(1) + v(2) + v(3)) overtone band of H2O perturbed by CO2 using near infrared diode laser spectroscopy

We report the CO2-induced broadening coefficients and line strength parameters of water vapor rovibrational transitions belonging to the (2ν1 + ν2 + ν3) overtone band measured by using an NIR diode laser spectrometer. Rotational quantum number dependence of the broadening coefficients is also shown. Use of balanced photodetector and wavelength modulation spectroscopy with small current modulation amplitude helped to obtain improved S/N ratio of the spectra. The recorded line shapes are fitted with standard Voigt profile by using a non-linear least squares fitting program to extract the line shape parameters. © 2008 Elsevier B.V. All rights reserved.

Measurement and analysis of rotational lines in the (2Î½1 + Î½2 + Î½3) overtone band of H2O perturbed by CO2 using near infrared diode laser spectroscopy

Argon-broadened lineshape parameters of the water vapour rovibrational transitions belonging to the (211)←(000) overtone band in the 818-834 nm wavelength region are measured by using a diode laser spectrometer. The first derivative signals of the overtone transitions have been recorded at different pressures of the perturber keeping the sample at its saturated vapour pressure at room temperature. Use of a balanced detector improves the S/N ratio of the spectra. The recorded lineshapes are fitted with standard Voigt line profiles in order to determine the linestrength and collisional broadening coefficient of 12 water vapour transitions. © 2005 Elsevier Inc. All rights reserved.

Journal of Molecular Spectroscopy

Lineshape study of argon broadened water vapour overtone transitions in the 818-834 nm wavelength region

A near-infrared tunable diode laser absorption spectrometer is set up to measure the air-induced broadening coefficients and the line-strength parameters of water-vapour overtone transitions within the (2, 1, 1) ← (0, 0, 0) band in the 822-832 nm wavelength region. A Hitachi HL8311 E double hetero-junction structure diode laser is used as a probe. The diode laser controller is home-built and stable within ±10 μA and ± 10 mK, respectively. The laser-head mount has a simple design and provides easy access whenever changing of the laser head is required. The diode laser emission wavelength is thermally tuned between 50 °C and 12 °C. Thermal tuning of the diode laser emission wavelength is used to reveal the mode structure of the diode laser and to probe the overtone-band transitions of water vapour within its operating wavelength range. Current tuning of the diode laser is used at a fixed laser temperature to study the transitions one at a time. A balanced detector is used to improve the S/N ratio of the spectrum. A phase sensitive detection technique is followed to obtain the first-derivative spectra of the overtone transitions. The first-derivative spectra have been recorded at different air pressures inside the sample cell while the water-vapour pressure is kept fixed. The first-derivative spectrum is numerically integrated to obtain the original line shape. The original line shape is fitted with a Voigt profile by using a nonlinear least-squares fit program to extract the air-broadening coefficient and the line-strength parameter. The data obtained in our work is compared with the results of the HITRAN database.

Applied Physics B: Lasers and Optics

Line-shape study of water vapour by tunable diode laser spectrometer in the 822-832 nm wavelength region

Measurement of pressure-dependent half-width of the rovibronic transitions of the oxygen A-band shows that the width remains almost unchanged at low pressure. Simulations based on soft collision model reveal that the collisional narrowing of the Doppler component compensates the pressure broadening up to a pressure of nearly 100 T. At higher pressure the line shape is non-Voigt type and has reduced but constant Doppler broadening. © 1997 Elsevier Science B.V.

Journal	Data powered by TypesetChemical Physics Letters
Publisher	Data powered by TypesetELSEVIER SCIENCE BV
ISSN	0009-2614