ABSTRACT A special technique is developed to measure the 13CO2/12CO2 isotope ratio in human breat... more ABSTRACT A special technique is developed to measure the 13CO2/12CO2 isotope ratio in human breath at atmospheric pressure with a 2 mum tunable diode laser. The procedure used to process the pressure-broadened spectra obtained and calculating the isotope ratio is based on a multidimensional linear regression of the spectra using simulated 13CO2, 12CO2, and H2O spectra. This technique allows the measurement of the delta-value for isotopic ratios with a precision of 0.070/00 within a data acquisition time of 3 min and a long-term reproducibility of 0.20/00.
A cavity ring-down spectroscopy with off-axis multipass cell and space separated detectors is sug... more A cavity ring-down spectroscopy with off-axis multipass cell and space separated detectors is suggested to record absorption spectrum without modulation of the diode laser intensity. The spectral resolution is ~0.0003 cm-1. The whole spectrum is obtained for a one continuous tuning of the laser frequency for ~20 ms. Apart from conventional CRDS a really needed rise time of the detectors are 1000 times slower. The recording of the whole spectrum for a one measurement give an additional possibilities of signal extraction at relatively high noise. The technique is applied to absorption measurement of NO2 in atmosphere.
ABSTRACT Diode laser spectroscopy with multipass cell and typically three channels are discussed.... more ABSTRACT Diode laser spectroscopy with multipass cell and typically three channels are discussed. In the first analytical channel a laser beam goes through multipass cell with a gas sample. In the second base-line recording channel the output laser intensity without absorption is recorded. The third reference channel is used for several additional aims. The information in all channels is used for analyzing and to improve a detection sensitivity. New technique of wavelength modulation is proposed with substation depress of residual amplitude modulation. The technique was applied to measure a background concentrations of NO2 and ratio of isotopes 12CO2/13CO2 in atmosphere.
A special shape of modulation of laser diode injection current is provided when the frequency mod... more A special shape of modulation of laser diode injection current is provided when the frequency modulation is not accompanied with amplitude modulation. Such approach permits to suppress essentially the influence of laser emission instabilities. When being applied to gas analysis it gives the possibility of long-term remote components monitoring. The stable relative absorptions of 8xl0-7 without special calibration are demonstrated. In combination with multipass cell (50 cm between the mirrors, 90 m optical length) it gives the absorption coefficient of l.2x10-10cm-1. As an example the daily evolution of atmosphere NO2 admixtures have been measured with a precision of O.5ppb.
27th International Symposium on Atmospheric and Ocean Optics, Atmospheric Physics, Dec 16, 2021
An implementation of laser absorption wavelength-modulation spectroscopy technique combined with ... more An implementation of laser absorption wavelength-modulation spectroscopy technique combined with quadrature detection of scattered radiation for remote monitoring of atmospheric industrial pollution by means of a compact lidar gas sensor, that may be installed at unmanned aerial vehicles, is presented. The instrument may be used for gas pipeline leak search and monitoring toxic gases near landfills, waste incinerators and other hazardous industries, analyze the internal atmosphere at industrial buildings and technological cycles control, providing sensitivity level of tens ppm*m at typical distances of tens meters. In order to increase the sensitivity of the device, in addition to temperature stabilization the laser radiation frequency is stabilized using a reference spectral absorption line of the selected gas.
We present new method of monitoring greenhouse gases using spectroscopic observations of solar ra... more We present new method of monitoring greenhouse gases using spectroscopic observations of solar radiation passed through the atmosphere with spectral resolution ΛvδΛ up to 108. Such a high resolution is achieved by heterodyne technique and allows to retrieve full information about spectral line shape which, in turn, is used to distinguish contribution of different atmospheric layers to the resulting absorption. Weak absorption line at 6056.5 cm-1 was selected for CO2 measurements and a quartet of lines centered at 6057 cm-1for CH4. The instrument setup includes Sun tracker with a microtelescope and chopper, diode DFB laser used as a local oscillator, a bundle of single mode optical fibers that provides medium for radiation transfer and beam coupling, reference cell with depressurized methane for LO frequency stabilization, and Fabry-Perot etalon for LO frequency calibration. A commercial p-i-n diode with squared detector replaces a mixer and IF spectrometer, providing measurement of heterodyne beating within a bandpass of few MHz, which determines the effective spectral resolution of the instrument. Spectral coverage within narrow range (about 1 cm-1) is provided by ramping the LO frequency based on feedback from the reference channel. Observations of Sun in the Moscow region have resulted for the first time in measurements of the atmospheric transmission near 1.65 μm with sub-Doppler spectral resolution. In order to retrieve vertical profiles of methane and carbon dioxide we developed the inversion algorithm implementing Tikhonov regularization approach. With measured transmission having S/N ratio of 100 or higher, the uncertainty of CH4 profile is about 10 ppb, with the uncertainty of CO2 profile at 1 ppm. This techniques is promising an affordable opportunity or widespread monitoring of greenhouse gases and may be implemented on existing ground-based stations. This work has been supported by the grant of Russian Ministry of education and science #11.G34.31.0074
The ratio of 12O2 and 13CO2 concentrations in the human exhaled air is measured by the method of ... more The ratio of 12O2 and 13CO2 concentrations in the human exhaled air is measured by the method of diode laser spectroscopy using a three-channel optical scheme and multipass cell. Unlike the previous measurements in the spectral range of ∼4.3 μm with a resolved rotational structure at low pressure of selected samples, the present measurements are performed in the range of
ABSTRACT A special technique is developed to measure the 13CO2/12CO2 isotope ratio in human breat... more ABSTRACT A special technique is developed to measure the 13CO2/12CO2 isotope ratio in human breath at atmospheric pressure with a 2 mum tunable diode laser. The procedure used to process the pressure-broadened spectra obtained and calculating the isotope ratio is based on a multidimensional linear regression of the spectra using simulated 13CO2, 12CO2, and H2O spectra. This technique allows the measurement of the delta-value for isotopic ratios with a precision of 0.070/00 within a data acquisition time of 3 min and a long-term reproducibility of 0.20/00.
A cavity ring-down spectroscopy with off-axis multipass cell and space separated detectors is sug... more A cavity ring-down spectroscopy with off-axis multipass cell and space separated detectors is suggested to record absorption spectrum without modulation of the diode laser intensity. The spectral resolution is ~0.0003 cm-1. The whole spectrum is obtained for a one continuous tuning of the laser frequency for ~20 ms. Apart from conventional CRDS a really needed rise time of the detectors are 1000 times slower. The recording of the whole spectrum for a one measurement give an additional possibilities of signal extraction at relatively high noise. The technique is applied to absorption measurement of NO2 in atmosphere.
ABSTRACT Diode laser spectroscopy with multipass cell and typically three channels are discussed.... more ABSTRACT Diode laser spectroscopy with multipass cell and typically three channels are discussed. In the first analytical channel a laser beam goes through multipass cell with a gas sample. In the second base-line recording channel the output laser intensity without absorption is recorded. The third reference channel is used for several additional aims. The information in all channels is used for analyzing and to improve a detection sensitivity. New technique of wavelength modulation is proposed with substation depress of residual amplitude modulation. The technique was applied to measure a background concentrations of NO2 and ratio of isotopes 12CO2/13CO2 in atmosphere.
A special shape of modulation of laser diode injection current is provided when the frequency mod... more A special shape of modulation of laser diode injection current is provided when the frequency modulation is not accompanied with amplitude modulation. Such approach permits to suppress essentially the influence of laser emission instabilities. When being applied to gas analysis it gives the possibility of long-term remote components monitoring. The stable relative absorptions of 8xl0-7 without special calibration are demonstrated. In combination with multipass cell (50 cm between the mirrors, 90 m optical length) it gives the absorption coefficient of l.2x10-10cm-1. As an example the daily evolution of atmosphere NO2 admixtures have been measured with a precision of O.5ppb.
27th International Symposium on Atmospheric and Ocean Optics, Atmospheric Physics, Dec 16, 2021
An implementation of laser absorption wavelength-modulation spectroscopy technique combined with ... more An implementation of laser absorption wavelength-modulation spectroscopy technique combined with quadrature detection of scattered radiation for remote monitoring of atmospheric industrial pollution by means of a compact lidar gas sensor, that may be installed at unmanned aerial vehicles, is presented. The instrument may be used for gas pipeline leak search and monitoring toxic gases near landfills, waste incinerators and other hazardous industries, analyze the internal atmosphere at industrial buildings and technological cycles control, providing sensitivity level of tens ppm*m at typical distances of tens meters. In order to increase the sensitivity of the device, in addition to temperature stabilization the laser radiation frequency is stabilized using a reference spectral absorption line of the selected gas.
We present new method of monitoring greenhouse gases using spectroscopic observations of solar ra... more We present new method of monitoring greenhouse gases using spectroscopic observations of solar radiation passed through the atmosphere with spectral resolution ΛvδΛ up to 108. Such a high resolution is achieved by heterodyne technique and allows to retrieve full information about spectral line shape which, in turn, is used to distinguish contribution of different atmospheric layers to the resulting absorption. Weak absorption line at 6056.5 cm-1 was selected for CO2 measurements and a quartet of lines centered at 6057 cm-1for CH4. The instrument setup includes Sun tracker with a microtelescope and chopper, diode DFB laser used as a local oscillator, a bundle of single mode optical fibers that provides medium for radiation transfer and beam coupling, reference cell with depressurized methane for LO frequency stabilization, and Fabry-Perot etalon for LO frequency calibration. A commercial p-i-n diode with squared detector replaces a mixer and IF spectrometer, providing measurement of heterodyne beating within a bandpass of few MHz, which determines the effective spectral resolution of the instrument. Spectral coverage within narrow range (about 1 cm-1) is provided by ramping the LO frequency based on feedback from the reference channel. Observations of Sun in the Moscow region have resulted for the first time in measurements of the atmospheric transmission near 1.65 μm with sub-Doppler spectral resolution. In order to retrieve vertical profiles of methane and carbon dioxide we developed the inversion algorithm implementing Tikhonov regularization approach. With measured transmission having S/N ratio of 100 or higher, the uncertainty of CH4 profile is about 10 ppb, with the uncertainty of CO2 profile at 1 ppm. This techniques is promising an affordable opportunity or widespread monitoring of greenhouse gases and may be implemented on existing ground-based stations. This work has been supported by the grant of Russian Ministry of education and science #11.G34.31.0074
The ratio of 12O2 and 13CO2 concentrations in the human exhaled air is measured by the method of ... more The ratio of 12O2 and 13CO2 concentrations in the human exhaled air is measured by the method of diode laser spectroscopy using a three-channel optical scheme and multipass cell. Unlike the previous measurements in the spectral range of ∼4.3 μm with a resolved rotational structure at low pressure of selected samples, the present measurements are performed in the range of
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