Dissociative recombination of molecular ions in the He–Ne plasma. Partial rate constants of atoms formation in the 2p 53d and 2p 54d configurations

Иванов, В. А.; Petrovskaya, A. S.; Skoblo, Yu. É.

doi:10.1134/s0030400x16020120

Cited by 3 publications

(1 citation statement)

References 23 publications

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“…Furthermore, based on experimentally determined vibrational relaxation rates reported in the literature, 35,36 the lifetime of the vibrationally excited He 2 + ion is on the order of a microsecond, 18 a time scale rather long compared to the plasma propagating speed, as will be discussed later in conjunction with time-resolved images. Based on the above argument along with the fact that multiple helium emission lines in plasma afterglows, with n = 3 and 4, have been traced back to dissociative recombination of vibrationally excited He 2 + , [35][36][37][38] we hypothesize that the He I emission outside the LTP torch in open, ambient air is the result of dissociative recombination of vibrationally excited He 2 + . Accordingly, the population of He 2 + ion in the open-air region can be inferred from the He I 706.5 nm emission.…”

Section: Two-dimensional Images Of Steady-state Ltp Emissionmentioning

confidence: 87%

Characterization of a Low-Temperature Plasma (LTP) Ambient Ionization Source Using Temporally Resolved Monochromatic Imaging Spectrometry

Chan,

Engelhard,

Wiley

et al. 2023

Appl Spectrosc

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The low-temperature plasma (LTP) probe is a common plasma-based source used for ambient desorption–ionization mass spectrometry (MS). While the LTP probe has been characterized in detail with MS, relatively few studies have used optical spectroscopy. In this paper, two-dimensional (2D) imaging at selected wavelengths is used to visualize important species in the LTP plasma jet. First, 2D steady-state images of the LTP plume for N2+ (391.2 nm), He I (706.5 nm), and N2 (337.1 nm) emissions were recorded under selected plasma conditions. Second, time-resolved 2D emission maps of radiative species in the LTP plasma jet were recorded through the use of a 200 ns detection gate and varying gate delays with respect to the LTP trigger pulse. Emission from He I, N2+, and N2 in the plasma jet region was found to show a transient behavior (often referred to as plasma bullets) lasting only a few microseconds. The N2+ and He I maps were highly correlated in spatial and temporal structure. Further, emission from N2 showed two maxima in time, one before and one after the maximum emission for N2+ and He I, due to an initial electronic excitation wave and ion–electron recombination, respectively. Third, the interaction of the LTP probe with a sample substrate and an electrically grounded metallic needle was studied. Emission from a fluorophore on the sample substrate showed an initial photon-induced excitation from plasma-generated photons followed by electronic excitation by other plasma species. The presence of a grounded needle near the plasma jet significantly extended the plasma jet lifetime and also generated a long-lived corona discharge on the needle. The effect of LTP operating parameters on emission spectra was correlated with mass-spectral results including reagent-ion signals. Lastly, five movies provide a side-by-side comparison of the temporal behavior of emitting species and insights into the interactions of the emission clouds with a sample surface as well as an external needle. Temporally and spatially resolved imaging provided insights into important processes in the LTP plasma jet, which will help improve analyte ion sampling in LTP–MS.

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