Investigation of the neon 2p collisional excitation transfer processes via CW laser collisionally induced fluorescence

Abstract

We present a method for determining the 2p (in Paschen notation) collisional excitation transfer coefficients in noble gases using continuous-wave laser collisionally induced fluorescence (CW LCIF, i.e. fluorescence from an upper level which is not that of the laser transition). The technique requires isolation of the specific 2p coupling process under examination, whereby that process provides an important and quantifiable contribution to the LCIF. This is achieved by selecting appropriate laser excitation and LCIF transitions. For a neon discharge operating at pressures ranging from 1.5 to 8.0 Torr and currents from 1 to 10 mA, 2p coupling is by ground-state atom collisions and the largest coupling exists between adjacent states. We show that in certain cases excitation transfer plays an important role in the excited-state kinetics.

Complementary optical diagnostics for determination of rate coefficients and electron temperatures in noble gas discharges

“…Analysis of several emission lines and populations (from absorption spectroscopy) provides a range of information and enhances the reliability of the determination. We have combined these widely used optical diagnostic techniques with related methods [9][10][11][12] which provide extensive information on the kinetics between the excited states, allowing sampling of the EDF across a wide range of electron energies.…”

Complementary optical diagnostic modelling of the argon positive column

“…The partial differentials are obtained using the expression for I jJ , the intensity of the 2p j -1s J transition, given in equation ( 4). The theoretical modelling and evaluation of all of these terms in equation ( 6) and their relative contributions are discussed in detail in our previous publications [6][7][8] for a number of different typical cases. Equation ( 6) may be solved to obtain the final expression [6]: where β jJ is the branching ratio from 2p j to 1s J , including collisional depletion routes and δ jJ is given by…”

“…The results we report here constitute part of ongoing development and application of our complementary approach to optical diagnostics of low-temperature plasmas based on the excited-state kinetics of noble gas atoms in the metastable and resonance states. In previous studies [6][7][8][9][10] we used the well-behaved neon positive column plasma to demonstrate the diagnostic power of combining two steady-state techniques (optical emission and absorption spectroscopy (OES and OAS)) with two CW laser-perturbed steady-state techniques (the optogalvanic effect (OGE) and laser collisionally induced fluorescence (LCIF)). In this work we describe our models for the argon 1s populations, emission line ratios and the CW LCIF spectra observed for laser excitation out of the 1s 5 state.…”

Energy Transfer Kinetics of the np5(n + 1)p Excited States of Ne and Kr

“…Therefore we consider collisions of Ne(2 p 5 3 p ) with He and Ne, where Penning ionization cannot occur. Ne(2 p 5 3 p ) + Ne collisions have been studied by several investigators. − Chang and Setser found that the 3 p [1/2] 1 level is quenched (loss to levels outside of the 2 p 5 3 p manifold) with a rate constant of 1.7 × 10 –11 cm 3 s –1 , which is too fast for the proposed application. Collisions between Ne(2 p 5 3 p ) and He have also been examined, ,,− but all of the state-to-state transfer measurements have focused on the higher energy levels (in part because the 632.8 nm line of the HeNe laser terminates on the 3 p ′[3/2] 2 level).…”