Absolute determination of local ground-state densities of atomic hydrogen in nonlocal-thermodynamic-equilibrium environments by two-photon polarization spectroscopy

Two-color, two-photon laser-induced polarization spectroscopy (LIPS) measurements of atomic hydrogen in near-adiabatic, atmospheric pressure hydrogen/air flames

“…Two-photon LIPS has been demonstrated for both atomic and molecular species such as nitrogen (N 2 ) [11], ammonia (NH 3 ) [12], carbon monoxide (CO) [12], and monatomic hydrogen (H) [13][14][15]. However, in these studies the pump and probe beam frequencies were the same.…”

“…The pressure dependence of LIPS signals has also been studied [17]. A theoretical treatment of LIPS in cases where the pump and probe have been tuned to the 1S-2S twophoton resonance of the H atom has been reported by Dux et al [13], although the hyperfine structure of the transition was not included in this treatment.…”

Determination of Two-Photon Absorption Cross-Section of Noble Gases for Calibration of Laser Spectroscopic Techniques

“…It has been used e.g. to determine absolute atomic hydrogen density in quite different environments with an uncertainty as low as 10% [5][6][7]. This precision can be by achieved by relative measurements with respect to a standard of atomic hydrogen density.…”

“…This precision can be by achieved by relative measurements with respect to a standard of atomic hydrogen density. The standard was established [7] at the Physikalisch-Technische Bundesanstalt (PTB), and it is based on the plasma generated in a stationary wallstabilized cascade arc operated with pure hydrogen, which was demonstrated to generate an ideal gas of atomic hydrogen for the experimental conditions. However, such a hydrogen density standard is quite complicated to be used in other laboratories, because it needs sophisticated technical equipment and requires some special operational experience.…”

Calculation of the spatial resolution in two-photon absorption spectroscopy applied to plasma diagnosis

“…Two-photon polarization spectroscopy 4 allows for direct measurement of the two-photon absorption and was used for measuring Stark broadening 1S-2S hydrogen, 5 for the determination of atomic hydrogen densities in a stationary wall stabilized cascaded arc plasma, 6 in a hollow cathode discharge (HCD) 7 and in atmospheric pressure flames, 8 and for the determination of local electric field (E-field) strength 9 as well. Two-photon induced Lyman-a fluorescence was employed in feasibility study for tokamak diagnostic 10 and Balmer-a fluorescence for local E-field strength determination in an optogalvanic cell.…”