This work is aimed to study of the ν1 band of the methane Raman spectrum in the pressure range of 1–80 atm. The wavenumber calibration was performed using the rotational–vibrational structure of the ν3 methane band. It was established, that pressure shift coefficient is about –0.02 cm–1 /atm, pressure broadening coefficient is about 0.005 cm– 1 /atm. According to the obtained experimental data, in the region of 2914–2916 cm–1 , with an increase in pressure, either the van der Waals methane complexes begin to make a noticeable contribution to the intensity of the ν1 band, or collision–induced Raman scattering increases in this range.
The work deals with the effects that lead to changes in Raman intensities of nitrogen and oxygen as their pressure increases. It was found that when these gases are compressed up to 80 atm, the intensities of their rovibrational Raman bands per molecule increased by approximately 3%. A theoretical model is proposed for describing Raman intensities in high-pressure gaseous media.
The present work focuses on the influence of CH4 environment on the changes in Raman spectra of n-C5H12 and i-C5H12 in the gaseous phase. It was found that in binary gas mixtures with an overwhelming content of CH4, the majority of the n-C5H12 and i-C5H12 Raman bands shifted toward lower wavenumbers. Moreover, there is also a redistribution of intensities between certain Raman bands of n-C5H12 and i-C5H12. The obtained results will be essential for Raman diagnostics of natural gas composition.
The study is dedicated to the problems of wavenumber calibration of multichannel Raman spectrometers. We present a calibration method based on the combined use of the neon emission spectrum and pure rotational lines of the hydrogen Raman spectrum.
Nowadays the sources of long-wavelength optical radiation (far infrared, terahertz range) are developed intensively. They have good perspectives in different fields of biology, medicine, security systems etc. This implies the need to have the detectors of radiation with advanced parameters 1,2. Golay cell 3 is one of the most sensitive detector types available at the time being despite, the strong development of semiconductor detectors 4 – 6. In Golay cell the energy is measured by the expansion of the gas in the sealed chamber: the gas absorbs the energy and presses the flexible membrane, thus the change of volume is registered. The disadvantages of these detectors are relatively high price, big size and vibration susceptibility. In our paper we consider the method of radiation detecting that is similar to one that is used in Golay cell but based on gas temperature measurement.
A possibility of applying SERS effect to enhance the intensity of the Raman spectra of gaseous media is investigated. More than 6-fold increase in Raman signals of the main components of air has been experimentally recorded due to increasing the electromagnetic field near an aluminum holographic diffraction grating. The average gain of Raman signals in the 30-nm layer at the grating – gaseous medium boundary was ~ 3×103.
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