2024
LIF study of hydride dissociation in electric discharges
DVOŘÁK, Pavel; Martina MRKVIČKOVÁ; Waseem KHAN; Nima BOLOUKI; Tomáš MEDEK et al.Základní údaje
Originální název
LIF study of hydride dissociation in electric discharges
Název česky
Fluorescenční studie disociace hydridů v elektrických výbojích
Autoři
DVOŘÁK, Pavel; Martina MRKVIČKOVÁ; Waseem KHAN; Nima BOLOUKI; Tomáš MEDEK; Adam OBRUSNÍK; Jan KRATZER; Milan SVOBODA a Jiří DĚDINA
Vydání
ESCAMPIG 2024 (The XXVI Europhysics Conference on the Atomic and Molecular Physics of Ionized Gases), 2024
Další údaje
Jazyk
angličtina
Typ výsledku
Vyžádané přednášky
Obor
10305 Fluids and plasma physics
Stát vydavatele
Česká republika
Utajení
není předmětem státního či obchodního tajemství
Odkazy
Označené pro přenos do RIV
Ano
Kód RIV
RIV/00216224:14310/24:00136513
Organizační jednotka
Přírodovědecká fakulta
Klíčová slova česky
fluorescence;LIF;plazma;DBD;hydridy;atomizace
Klíčová slova anglicky
fluorescence;LIF;plasma;DBD;hydrides;atomization
Příznaky
Mezinárodní význam, Recenzováno
Změněno: 2. 9. 2024 08:30, doc. Mgr. Pavel Dvořák, Ph.D.
V originále
The fact that plasma is able to dissociate number of molecules is the basis for number of plasma applications including applications in analytical chemistry, where plasma is used for the dissociation of volatile compounds, frequently hydrides, which are used as carrier molecules for number of toxic, hazardous or biogenic elements. Recently, dielectric barrier discharges (DBDs) have been systematically studied as atomizers, i.e. as a tool for the decomposition of hydrides or other volatile molecules. The situation in DBDs is relatively complicated, because the volume dissociation of hydrides combines with surface reactions on walls, which can lead to unwanted losses of analyte atoms or be used for in-situ preconcentration of analytes and to improve the detection limit of the analytical methods. Our work is a systematic (TA)LIF study of reactive species in various atomizers, including both the dominant radicals originating from the main plasma gases (i.e. atomic hydrogen, atomic oxygen, OH radicals) and various free analyte atoms (Pb, Te, Bi, Se, Sn, Ge, Sb). In order to increase the LIF signal-to-noise ratio, we developed a LIF method based on partially saturated fluorescence and verified it by comparison with absorption measurements. The laser-based diagnostics on discharge-based atomizers were supplemented by E-FISH measurements of the electric field in the discharge. Experimental results were complemented by a numerical model of the plasma chemistry and gas flow in the atomizers. Regarding the atomization mechanisms, we confirmed the theory that the decomposition of hydrides in both plasma and flame atomizers is based on reactions with atomic hydrogen, we revealed differences in spatial distribution of various analytes demonstrating the important role of the surface reactions, ex- plained the difference of the performance of various atomizers, observed the preconcentration of analyte atoms on the wall and explained why a small (i.e. significantly substoichiometric) amount of oxygen manages to initiate the preconcentration on walls. As an example of LIF measurements, the distribution of free Sb atoms in a DBD atomizer can be discussed, when stibine (SbH3) from a 1 ng/l-solution was supplied to the plasma together with Ar and H2. The results obtained with a continuous supply of SbH3 reveal a nearly homogeneous distribution of free Sb atoms through the whole active discharge (−25 to +25 mm). The homogeneous distribution of Sb atoms through the whole reactor and the relatively high Sb concentration demonstrate a good performance of the DBD for atomization of SbH3. It was possible to preconcentrate the analyte (Sb) on reactor walls, which led to an increase of the fluorescence signal by more than an order of magnitude. The release of Sb from the walls had a character of a wave travelling from the discharge center towards its edges. The strong increase of Sb concentration demonstrate the possibility to control the surface reactions and use them for analyte preconcentration and improvement of the detection limit of studied species in DBD-based atomizers.
Česky
Přenáška nejprve diskutovala problematiku metody laserem indukované fluorescence (LIF) včetně řešení problematických situací, jako jsou saturace fluorescenčního procesu, rychlé zhášení, fotodisociace excitovaného stavu a přenos exitace do detekovaného zářivého stavu. Druhá část přednášky aplikovala metodu LIF (a další výzkumné metody, vč. simulace výboje) na problematiku disociace částic ve výbojích, zejména v dielektrických bariérových výbojích (DBD). Důraz byl položen zejména (ale nejenom) na disociaci molekul těkavých hydridů.
Návaznosti
| GF23-05974K, projekt VaV |
| ||
| LM2023039, projekt VaV |
|