Optogalvanic spectroscopy

Barbieri, Beniamino; Beverini, N.; Sasso, Antonio

doi:10.1103/revmodphys.62.603

Cited by 193 publications

(104 citation statements)

References 264 publications

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“…U OG =U P . In terms of the plasma, such a perturbation correlated to a perturbation of T e and/or n e , but since the low-energy IR photons of the laser could be expected to only excite rovibrational transitions in the target molecules and not alter their electronic states [8], it was assumed that temperature perturbations, T e , dominated over density perturbations, n e , i.e., T e /T e >>n e /n e [22]. Assuming the perturbations to be small, i.e.…”

Section: Theorymentioning

confidence: 99%

“…In the IR spectrum, the laser-sample interactions are dominated by excitations of higher order rovibrational states in the sample molecules. In such a system, the OG signal primarily stems from the collisional de-excitation of these states back to the ground level, which, in turn, affects the impedance of the plasma [8]. OG spectroscopy was a hot research topic in the late 1970s and early 1980s, when OG detectors were routinely used as, e.g., feedback sensors in gas lasers [8].…”

Section: Introductionmentioning

confidence: 99%

“…In such a system, the OG signal primarily stems from the collisional de-excitation of these states back to the ground level, which, in turn, affects the impedance of the plasma [8]. OG spectroscopy was a hot research topic in the late 1970s and early 1980s, when OG detectors were routinely used as, e.g., feedback sensors in gas lasers [8]. However, they did not find lasting applications in IR spectroscopy, mostly due to the lack of reliable light sources at relevant wavelengths at the time.…”

Section: Introductionmentioning

confidence: 99%

“…Instead of studying the sample by measuring the transmitted light intensity and, consequently, the absorbance of the sample, as is customary in current IR absorption spectroscopy, an OG detector studies the sample by investigating the effect of laser-sample interactions on the impedance of a plasma inside the sample cell [8]. In the IR spectrum, the laser-sample interactions are dominated by excitations of higher order rovibrational states in the sample molecules.…”

Section: Introductionmentioning

confidence: 99%

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Improved optogalvanic detection with voltage biased Langmuir probes

Persson

Berglund

Salehpour

2014

Journal of Applied Physics

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Optogalvanic detectors show great potential for infrared spectroscopy, especially in cavity enhanced techniques where they, in contrast to ordinary absorption detectors, can perform intracavity measurements. This enables them to utilize the signal-to-noise ratio improvement gained from the extended effective path length inside an optical cavity, without losing signal strength due to the limited amount of light exiting through the rear mirror.However, if optogalvanic detectors are to become truly competitive, their intrinsic sensitivity and stability has to be improved. This, in turn, requires a better understanding of the mechanisms behind the generation of the optogalvanic signal. The study presented here focuses on an optogalvanic detector based on a miniaturized stripline split-ring resonator plasma source equipped with Langmuir probes for detecting the optogalvanic signal. In particular, the effect of applying a constant bias voltage to one of the probes is investigated, both with respect to the sensitivity and stability, and to the mechanism behind the generation of the signal. Experiments with different bias voltages at different pressures and gas composition have been conducted. In particular, two different gas compositions (pure CO 2 and 0.25% CO 2 in 99.75% N 2 ) at six different pressures (100 Pa to 600 Pa) have been studied. It has been shown that probe biasing effectively improves the performance of the detector, by increasing the amplitude of the signal linearly over one order of magnitude, and the stability by about 40% compared with previous studies. Furthermore, it has been shown that relatively straightforward plasma theory can be applied to interpret the mechanism behind the generation of the signal, although additional mechanisms, such as rovibrational excitation from electron-molecule collisions, become apparent in CO 2 plasmas with electron energies in the 1-6 eV range. With the achieved performance improvement and the more solid theoretical framework presented here, stripline split-ring resonator optogalvanic detectors can evolve into a compact, inexpensive and easy-to-operate alternative for future infrared spectrometers.

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Section: Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Improved optogalvanic detection with voltage biased Langmuir probes

Persson

Berglund

Salehpour

2014

Journal of Applied Physics

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“…Optogalvanic (OG) spectroscopy [4][5][6] is expected to be highly sensitive for the visible and near-infrared transition lines of non-metallic elements. 7,8 The OG effect originates from a change in the impedance in a steady state glow-discharge when the discharge medium resonantly absorbs radiation.…”

Section: Introductionmentioning

confidence: 99%

One and Two-photon Excited Optogalvanic Spectra of Argon in the Wavelength Region of 735 – 850 nm

2010

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Optogalvanic (OG) spectra of argon in the visible to near-infrared spectral region between 735 and 850 nm were investigated using a Grimm-style glow-discharge tube, which has been widely used to obtain depth profiles of the elemental composition on various film-like samples. About 49 lines of one-photon and two-photon OG peaks were observed with a pulsed Ti:sapphire laser; these peaks were precisely assigned. Two-photon OG spectra of argon were easily observed without focusing the pulsed laser irradiation to more than 1 mJ. The excitation mechanisms of the observed argon OG spectra could be classified into 3 types: single-photon transition, two-photon transition, and twophoton stepwise transition. In addition, a pseudo-resonant effect was also found to be effective. The argon lines observed in this experiment are suitable as convenient calibration wavelength markers of pulsed tunable laser radiation.

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Spectroscopy, Laser

Inguscio

Sasso²

2003

Digital Encyclopedia of Applied Physics

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Optogalvanic spectroscopy

Cited by 193 publications

References 264 publications

Improved optogalvanic detection with voltage biased Langmuir probes

Improved optogalvanic detection with voltage biased Langmuir probes

One and Two-photon Excited Optogalvanic Spectra of Argon in the Wavelength Region of 735 – 850 nm

Spectroscopy, Laser

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