Single-mode 3.39 μm laser study of methane absorption lineshape

A single-mode, HeNe 3.39 μm laudy has been made of the overlapping P(7)₁, v₃ methane line. The Galatry lineshape (involving collision-narrowing) is clearly verified, and the temperature dependence of the collision-broadened linewidth is at T^{?0.69 ± 0.4}, as opposed to our previous determination of ～T^?1.     

Speckle phenomena at 10 micron wavelength

Naturally occurring solid surfaces display structure over wide ranges of spatial wavelength, and this has important influences upon their radiation scattering characteristics. Fluctuations in scattered intensity are less severe than for smoothly-profiled surfaces, but the fine structure of the surface enhances scattering through large angles. Laboratory measurements of scattering of 10.6 micron CO₂ laser radiation by roughened surfaces are used to illustrate these effects and show the extent to which they may be modelled using physical optics.     

Measurement technique for methane concentration by wavelength scanning of a distributed-feedback laser

A new technique which takes advantage of distributed-feedback (DFB) laser wavelength scanning to measure methane concentration is presented. A wavelength scan of the methane absorption peak at 1665.9 nm is realized using sawtooth modulation of the current injected to a DFB laser. A reference methane gas cell is used to find the methane absorption peak around 1666 nm, and normalization is used to reduce outside influences such as power drift and fiber loss. The concentration is derived by arithmetic processing of the absorption coefficient of the methane gas. An application test is carried out in a coal mine and a long-term precision of 0.05% is achieved.     

An anomalous Zeeman effect in methane at 3.39 μm

The present paper reports on the first observation of an anomalous Zeeman effect on the hyperfine components of theF ₂ ⁽²⁾ line in methane (λ=3.39 μm), on an asymmetry of a nonlinear resonance in the magnetic field due to the influence of recoid, and on measurements of shifts of individual hyperfine components in weak magnetic fields.     

Effect of a transverse magnetic field on the power and polarization of the radiation of a helium-neon laser at a wavelength of 3.39 μ

The dependence of the power and polarization of the radiation of a helium-neon laser on the value of a transverse magnetic field is studied. The effect of changes in the Q of the resonator under these conditions is also investigated. It is shown that it is possible for circularly polarized radiation to exist in a laser with Brewster windows.     

Collision broadening of the 3.39 μm methane line

Zeitschrift für Physik A Hadrons and nuclei - Collision broadening of the 3.39 μm methane line is investigated experimentally using saturated absorption spectroscopy and theoretically by...     

High-temperature absorption coefficient of methane at 3.392μ

The spectral absorption coefficient of methane at 3.392μ has been measured in the temperature range 965 ?T, °K≤2710 behind incident and reflected shock waves. It is given by the relation P'=P'₀(T₀/T)ⁿ where P'₀=(1.34±0.58)x10²cm^-1atm^-1 at T₀=300°K and n=2.88±0.21. The empirically determined temperature exponent n may be approximately accounted for by a simplified theoretical analysis.     

Frequency stability and reproducibility of the 3.39 μm He−Ne laser stabilized on the methane line

Physical factors determining the frequency reproducibility of a gas laser with nonlinear absorption are analyzed. On the basis of experimental and theoretical results it is shown that the collisional shift, the second-order Doppler effect, the recoil effect, and the magnetic hyperfine structure do not reprsent the limitation in achieving a frequency reproducibility of the order of 10^?13?10^?14. This paper reports on experiments achieving frequency stability of 5·10^?15 and reproducibility of 3·10^?14 for the 3.39 μm He?Ne laser with an internal methane cell.     

Continous coherent radiation in methane at λ=3.39 μm in spacially separated fields

Continuous coherent radiation in a gas observed in a spacially separated standing wave fields is reported for the first time. The radiation was observed in the center of lineF ₂ ⁽²⁾ in methane at the interaction of atoms with two standing waves separated by the distance of 3.5 cm.     

Spectroscopic study of laser irradiated chromatin

Antiprotonic helium is a metastable three-body neutral atom consisting of an antiproton, a helium nucleus and an electron, which we serendipitously discovered some 20 years ago. The antiproton, which normally annihilates within a few picoseconds when injected into matter, can be “stored” in this system for up to several microseconds, and laser spectroscopy is possible within this time window. From the laser transition frequency, the antiproton-to-electron mass ratio can be deduced to high precision. Recent progress at CERN’s antiproton decelerator (AD) will be discussed.     

可调谐半导体激光吸收光谱法对高温甲烷的测量研究

可调谐半导体激光吸收光谱(TDLAS)是一种具有高灵敏度、高分辨率、快速检测特点的气体检测技术,已广泛用于大气中多种痕量气体的检测以及地面的痕量气体和气体泄漏的检测。研究了利用TDLAS技术测量高温下甲烷浓度的实验方法,使用可加热的静态吸收池对在1653.72nm波长附近R(3)支转动跃迁的吸收线进行了测量,并计算了吸收线强。分别在相同温度不同浓度和相同浓度不同温度的两种条件下进行了实验。结果表明,利用直接吸收的方法,在实验室可以得到370K时的最小可探测限为100×10-6,500K时的最小可探测限为245×10-6(吸收池长度为10cm),可以应用在燃烧控制及喷焰气体浓度测量等多个领域。