Laser-Induced Fluorescence of Xe I and Xe II in Ambipolar Plasma Flow

Laser-induced fluorescence diagnostic technique is applied here to probe xenon neutrals and single-charged ions in an ambipolar plasma source. A single tunable diode laser is employed for pumping both following transitions: 6s
²
[1/2]
₁
⁰
-6p
²
[3/2]
₁
⁰
(centered at 834.68 nm; air) and 5d[4]
_7/2
-6p[3]
_5/2
(centered at 834.72 nm; air), for Xe I and Xe II detection, respectively. The corresponding decay states are 6s[3/2]
₁
⁰
and 6s[2]
_3/2
leading to fluorescence signal at 473.415 and 541.915 nm, respectively. A detailed description of the experimental setup along with time-averaged fluorescence signals are presented, demonstrating the possible application of the above adjacent pumping wavelengths in xenon ambipolar plasmas for probing both ions and neutrals under various operating conditions. A comprehensible discussion to what extent the registered laser-induced fluorescence signals mirror velocity distribution functions is realized, following hyperfine splitting and isotopic shift analysis.