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Application of Diode Laser Molecular Absorption Spectroscopy for Studies of Gas Concentrations in Food Packages

Von Keitz, Jan LU (2014) FYSK01 20141
Department of Physics
Atomic Physics
Abstract (Swedish)
When it comes to absorbing and emitting radiation, molecules show similar properties as atoms
do. A signicant dierence though, is that a molecular spectrum consists of notably more
absorption lines compared to an atomic spectrum. The additional lines appear due to the fact
that molecules can not only exist in electronic, but also in vibrational and rotational energy
states. Each gas has uniquely dened absorption lines, which makes it possible to associate
a ngerprint to the gas. Molecular spectroscopy enables to scan over these lines to determine
the existence of a specic gas. With, for example, the help of Tunable Diode Laser Absorption
Spectroscopy (TDLAS), which has been used in this work, and by applying the Beer-Lambert
law,... (More)
When it comes to absorbing and emitting radiation, molecules show similar properties as atoms
do. A signicant dierence though, is that a molecular spectrum consists of notably more
absorption lines compared to an atomic spectrum. The additional lines appear due to the fact
that molecules can not only exist in electronic, but also in vibrational and rotational energy
states. Each gas has uniquely dened absorption lines, which makes it possible to associate
a ngerprint to the gas. Molecular spectroscopy enables to scan over these lines to determine
the existence of a specic gas. With, for example, the help of Tunable Diode Laser Absorption
Spectroscopy (TDLAS), which has been used in this work, and by applying the Beer-Lambert
law, also the gas concentration can be obtained. Nevertheless, for a precise calculation of the gas
concentration the path length travelled by light needs to be available. This especially can cause
diculties when turbid materials are examined, in which the light scatters a lot, and therefore
the dimension of the sample does not correspond to the path length of the light anymore.
This work includes the examination of food packages lled with modied atmosphere. Diode
lasers emitting wavelengths around 760 nm and 2054 nm are used to scan over an absorption
line of oxygen and carbon dioxide, respectively. First, it is presented how the carbon dioxide
concentration of 75 % in a sealed bread rolls package is obtained. Afterwards TDLAS combined
with a technique called Wavelength Modulation Spectroscopy (WMS), which allows to detect
low absorption signals, is used to perform a time dependent measurement on a package with
ageing milk inside. The carbon dioxide and oxygen concentrations are monitored simultaneously
over 5 days. With the relation between the two concentrations it is possible to speculate about
biological activity in the milk package. Another important aspect is, that all the measurements
are done non-intrusively, which leaves the package intact allowing usage after the measurement.
2 (Less)
Please use this url to cite or link to this publication:
author
Von Keitz, Jan LU
supervisor
organization
course
FYSK01 20141
year
type
M2 - Bachelor Degree
subject
keywords
Diode Laser Spectroscopy Gas Concentration Food Packages
language
English
id
4463371
date added to LUP
2014-06-22 17:31:28
date last changed
2014-10-22 10:06:52
@misc{4463371,
  abstract     = {{When it comes to absorbing and emitting radiation, molecules show similar properties as atoms
do. A signicant dierence though, is that a molecular spectrum consists of notably more
absorption lines compared to an atomic spectrum. The additional lines appear due to the fact
that molecules can not only exist in electronic, but also in vibrational and rotational energy
states. Each gas has uniquely dened absorption lines, which makes it possible to associate
a ngerprint to the gas. Molecular spectroscopy enables to scan over these lines to determine
the existence of a specic gas. With, for example, the help of Tunable Diode Laser Absorption
Spectroscopy (TDLAS), which has been used in this work, and by applying the Beer-Lambert
law, also the gas concentration can be obtained. Nevertheless, for a precise calculation of the gas
concentration the path length travelled by light needs to be available. This especially can cause
diculties when turbid materials are examined, in which the light scatters a lot, and therefore
the dimension of the sample does not correspond to the path length of the light anymore.
This work includes the examination of food packages lled with modied atmosphere. Diode
lasers emitting wavelengths around 760 nm and 2054 nm are used to scan over an absorption
line of oxygen and carbon dioxide, respectively. First, it is presented how the carbon dioxide
concentration of 75 % in a sealed bread rolls package is obtained. Afterwards TDLAS combined
with a technique called Wavelength Modulation Spectroscopy (WMS), which allows to detect
low absorption signals, is used to perform a time dependent measurement on a package with
ageing milk inside. The carbon dioxide and oxygen concentrations are monitored simultaneously
over 5 days. With the relation between the two concentrations it is possible to speculate about
biological activity in the milk package. Another important aspect is, that all the measurements
are done non-intrusively, which leaves the package intact allowing usage after the measurement.
2}},
  author       = {{Von Keitz, Jan}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Application of Diode Laser Molecular Absorption Spectroscopy for Studies of Gas Concentrations in Food Packages}},
  year         = {{2014}},
}