Optogalvanic Laser Spectroscopy (original) (raw)
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Progress in Optical Science and Photonics, 2014
In this chapter we will discuss the laser optogalvanic effect in a discharge plasma environment, specifically associated with an iron-neon (Fe-Ne) hollow cathode lamp. The history of the optogalvanic effect will serve as an introduction to the importance of the phenomena. The theoretical model behind the optogalvanic effect will provide insight into the importance of laser optogalvanic spectroscopy as a tool for spectral characterization of the plasma processes and enhanced understanding of the collisional state dynamics associated with the discharge species in hollow cathode lamps. The present chapter will focus on transition states of neon in the Fe-Ne hollow cathode lamp. The results presented here will use, for illustrative purposes, the waveforms associated with the laser-excited optogalvanic transitions of neon: 1s 4-2p 3 (607.4 nm), 1s 5-2p 7 (621.7 nm), 1s 3-2p 5 (626.6 nm), 1s 5-2p 8 (633.4 nm) and 1s 5-2p 9 (640.2 nm). A comparison between the experimentally recorded optogalvanic signal waveforms and the Monte Carlo fitting routine, along with a discussion related to the variation of the (a i and b j) fitting coefficients as a function of the discharge current, will illustrate the success of our theoretical model. We will also briefly touch upon the potential applications of the optogalvanic effect at the nanoscale in fields such as graphene-based nanoelectronics and nanoplasmonics.
Optogalvanic effect in a hollow cathode discharge with nonlaser sources
Applied Optics, 1982
Several atomic emission sources were investigated for their potential to induce optogalvanic signals in hollow cathode lamps. The sources included an inductively coupled argon plasma, a H 2 -0 2 flame, a high-temperature furnace, electrodeless microwave discharge lamps, and hollow cathode lamps. Successful results were obtained with argon emission from the inductively coupled plasma focused into an argon-filled hollow cathode tube and with atomic emission from one hollow cathode discharge focused into a hollow cathode tube containing the same element. Very low level optogalvanic signals were observed from the other sources but could not be unambiguously ascribed to emission from a specific element. A problem encountered was the presence of a background signal due cathode.
Laser spectroscopy of calcium in hollow-cathode discharges
Journal of the Optical Society of America B, 2001
We investigated the use of hollow-cathode discharges for high-resolution and high-sensitivity spectroscopy, using atomic calcium. Spectra with sub-Doppler resolution of CaI transitions at 423 (resonant), 610, 612, 616, 645, 657 (intercombination), and 672 nm were obtained by optogalvanic saturation spectroscopy in lamps filled with argon (0.6 and 2.5 Torr) and krypton (0.6 Torr). A Doppler background that is due to velocity-changing collisions, which may severely limit the resolution, can be greatly reduced by the choice of buffer gas. Sub-Doppler linewidths comparable with those achieved in atomic beams have been obtained, making a properly chosen hollow-cathode lamp a convenient tool for high-resolution spectroscopic experiments, providing wavelength references for laser frequency tuning. The sensitivity of optogalvanic detection and the excitation of most electronic levels by the discharge make these lamps attractive also for investigating weak and excited level transitions with the use of a simple experimental setup.
laser-induced optogalvanic effect in pre-breakdown discharges
Mode-structure influences on the laser-induced optogalvanic effect in pre-breakdown discharges, 1994
The technique of quantitative laser-induced optogalvanic perturbation of pre-breakdown discharges, established in previous work, is developed through an investigation of the effect of the mode structure of the laser radiation. Results are presented using three different mode structures: single mode and two qualitatively different multimode structures. These show that one of the multimode structures, readily generated by a ring dye laser, is unsuitable for quantitative optogalvanic investigations. The other controlled multimode structure gives results broadly similar to those from single-mode perturbation. However, optogalvanic signals are harder to locate with single-mode perturbation and metastable-particle-density decay rates are higher, for a given laser intensity, thus making analysis more difficult. Also, effects possibly due to saturation become apparent at relatively low laser intensities with single-mode perturbation. Both multimode and single-mode perturbation show effects with variation of laser intensity that are not in accordance with existing theoretical expectations. These effects might be due to a subset of the Is, metastable population being unable to absorb the laser radiation, because of its polarization state. This implies that the magnetic substates of the 1% state are surprisingly resilient to collisional redistribution of population among them.
1998
Good signal-to-noise ratio optogalvanic effect (OGE) has been obtained in a hollow cathode discharge using commercially available low cost and low power diode lasers emitting in the visible region of the spectrum. The OG profiles of Ne and HE transitions suitable for diode laser wavelength locking to absolute reference have been studied. The amplitude and sign of the optogalvanic signal (OGS) have been measured simultaneously with the absorption in dependence on the laser power an the gas discharge parameters in order to find the conditions for optimum OGS.