Measurement of vibrational, gas, and rotational temperatures of H2 (X1Σg+) in radio frequency inductive discharge plasma by multiplex coherent anti-Stokes Raman scattering spectroscopy technique

Abstract

Translational, rotational, and vibrational temperatures of H2 in radio frequency inductive discharge plasmas at pressures and power release ranges, respectively, of 0.5–8 torr and 0.5–2W∕cm3 have been measured by using multiplex coherent anti-Stokes Raman scattering (CARS) spectroscopy. Computational codes have been developed to determine the rotational and vibrational temperatures and to analyze H2 CARS spectrum for nonequilibrium conditions. The results show a decrease of the vibrational temperature from 4250 to 2800 K by increasing the pressure from 0.5 to 8 torr and a corresponding increase of the rotational temperature from 525 to 750 K.

Atom and Ion Chemistry in Low Pressure Hydrogen DC Plasmas

“…Many studies have also been devoted to the atomic hydrogen produced in these plasmas, which is of relevance for film deposition processes. [5][6][7][8] The dynamics of internally excited states of H 2 [9][10][11][12][13][14][15][16][17][18] and its close relationship to the production of H -ions by dissociative electron attachment have been also addressed by various groups. [19][20][21] Theoretical and experimental investigations over decades have provided much information on fundamental processes relevant to H 2 plasmas (see for instance refs 22-27 and references therein), but there is still a dearth of basic data specially on state-resolved cross sections and on gas surface interactions, and many uncertainties remain about the coupling between the plasma chemistry and the discharge dynamics.…”

From cold to fusion plasmas: spectroscopy, molecular dynamics and kinetic considerations

“…In this paper we report a sample of results recently obtained by our group under RF inductive plasma conditions [13,14] as well as the theoretical model used for rationalizing the results.…”

“…The experimental set-up included the RF inductive discharge plasma reactor and vacuum chamber for CARS technique calibration, a system for gas feeding and pumping out, a pressure controlling system, the CARS system with optics to recombine and focus the pump laser beams for generating the CARS spectrum, an automatic system for data acquisition and processing [14]. The longitudinal, tube-type, RF configuration (diameter 3.2 cm and 54 cm length) was designed to achieve large concentrations of vibrationally excited H 2 .…”

“…Figure 1 shows average values of the rotational temperature, T rot , and vibrational temperature, T 1→0 , as function of the total pressure in the RF inductive discharge plasma in the molecular hydrogen for various power releases. The experimental data were evaluated from the CARS spectra processing, as illustrated in [14]. These CARS spectra were taken from the probe volume positioned on the axis and in the central zone of the RF inductive coil. )…”

“…These CARS spectra were taken from the probe volume positioned on the axis and in the central zone of the RF inductive coil. ) as a function of pressure, in RF inductive discharge plasma [14].…”