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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 1:48 |
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Conference: Bucharest University Faculty of Physics 2010 Meeting
Section: Optics, Spectroscopy, Plasma and Lasers
Title:
A set-up for alcohol vapours detection using 3,3922 micron He-Ne laser radiation
Authors:
M. Ristici, I. Gruia, B. Ionita, M. Rosu
Affiliation:
University of Bucharest, Faculty of Physics
E-mail
gruia_ion@yahoo.com
Keywords:
Abstract:
A very well known laser oscillation is 3,3922 micron wavelength of He-Ne plasma. It was obtained in 1963 by Mloom and was studied wanly for its competition with the red 633 nm line. The nearly coincidence with a major absorption band for detection of substances containing such bands. The ethyl alcohol is an example. The molecule have five such bands so that the absorption is consistent. Many trying were made to develop an apparatus for detecting and measuring the alcohol vapour in breath of motor vehicle drivers.
As a result of our research on He-Ne, we developed a low power 3,3922 micron laser to be used in detection experiments of substances containing C-H bands.
As a recipient for vapours we used a glass cell designed to be used inside the laser resonator. It is a glass cylinder Brewster angle ended. The cell has a reservoir of ethyl alcohol, temperature controlled.
A He-Ne laser oscillating simultaneously at 3,3922 micron and 633nm was used as a sensible detector for the presence of vapour an cell. The pressure of vapours is evaluated taking account of cell temperature. The measured optical power of 633 nm laser radiation depends on the absorbing vapour pressure of ethyl alcohol on the cell, because the two laser lines have the same higher laser level so that they are competitive.
In the presence of alcohol vapours within the cavity of He-Ne laser, the infrared radiation was absorbed and the 633 nm radiation was enhanced at the expense of the 3,39 micron radiation.
The set-up that we described is destined for experiments in laser physics laboratory for students.
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