Electronic-energy exchange cross sections for Ar* (3P) and N2(X 1Σg+)

Abstract

Differential cross sections for Ar* (3P) scattered by N2(X 1Σg+), obtained at 0.051 eV using crossed molecular beams, are reported from 4° to 174° c.m. A rainbow maximum is observed at 6.3° c.m. The small-angle elastic scattering is analyzed to obtain parameters for a double-Lennard-Jones potential. At large angles the cross sections are depleted by exchange scattering. The exchange probabilities are obtained by subtracting the experimental cross sections from elastic scattering cross sections calculated from the double-Lennard-Jones parameters. The resulting total exchange cross section and threshold energy are σex = 11.8±3.5 Å, E0=0.0081±0.001 eV. Comparison with cross sections deduced from published rate constants indicates that σex increases with initial relative kinetic energy from threshold to 0.051 eV.

Molecular beam study of the collisions of state-monitored, metastable noble gas atoms with O2(X 3Σg−)

“…1͑c͒ Our value of Q is in excellent agreement with the value of 11.8 Å 2 obtained in a crossed-beam, differentialscattering apparatus at virtually the same collision energy. 27 Beijerinck and co-workers 28 recently measured *(g) for the C-state product over a large velocity range and summarized the earlier experimental measurements of that cross section. One historical issue is the value of the C-state excitation branching fraction, ⌫*ϭ*/ Q .…”

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“…In addition, in Ar/N 2 plasmas, excitation transfer with Ar m has been reported to be an additional pathway to populate N 2 ðC 3 P u Þ states, which eventually cascade to the N 2 ðA 3 S þ u Þ state. [52,55,65,72] The two emission spectra in Figure 6b and c, which correspond to different N 2 flow rates, qualitatively appear to be very similar in terms of the observed emission lines. However, the relative line intensities corresponding to the second positive and first negative systems are $1.5 times greater in Figure 6c (50 sccm N 2 ) compared to those in Figure 6b (25 sccm N 2 ).…”

“…The first positive band system of N 2 typically emits over the range of 500–1100 nm, and these bands have been attributed to transitions from the second excited state ( B ) to the first excited state ( A ) via the transition . The metastable state is also populated via direct electron impact from the ground state ( X ), , and is particularly important due to its long radiative decay lifetime of 1–2 s . It is therefore, expected to be the predominant gas‐phase molecular species involved in surface nitridation.…”

“…While processes (a) and (b) only involve N 2 species, process (c) may be the one that is responsible for the reported increase in density upon Ar dilution of N 2 plasmas. In addition, in Ar/N 2 plasmas, excitation transfer with Ar m has been reported to be an additional pathway to populate states, which eventually cascade to the state …”

“…N 2 ðA 3 S þ u ; y 00 Þ. The metastable N 2 ðA 3 S þ u Þ state is also populated via direct electron impact from the ground state (X), N 2 ðX 1 S þ g Þ, [55,60,62,63] and is particularly important due to its long radiative decay lifetime of 1-2 s. [55,61,65] It is therefore, expected to be the predominant gas-phase molecular species involved in surface nitridation. Emission lines observed over the range of 300-490 nm are related to the second positive band system of N 2 , [63,64] which is the radiative transition system from the third excited state (C) to the second excited state (B), N 2 ðC 3 P u ; y 0 Þ !…”