Excitation Of N2 Research Articles

Adiabatic reactions on excited electronic states of N[formula omitted]O: First computations on the O([formula omitted]P)+N[formula omitted](X)[formula omitted]N([formula omitted]D)+NO(X) and O([formula omitted]P)+N[formula omitted](A)[formula omitted] N([formula omitted]S)+NO(X) reactions

Electronically excited nitrogen atoms and N2 molecules play a major role in nitrogen-rich atmospheres, specially under extreme conditions. Here we computationally explore several excited states of the N2O system and identify two new reactions involving the excited species N2(A) and N(2D) that can occur without electronic transitions. Their rate coefficients are estimated for the first time, and their implication to atmospheric models are discussed. We infer that the O(3P)+N2(A)→N(2D)+NO(X) channel should account for the total experimental NO production at room temperature.

Improvement of SAMI2 with Comprehensive Photochemistry at Mid-Latitudes and a Preliminary Comparison with Ionosonde Data

Photochemistry can significantly affect the ionospheric status. Adopting a comprehensive photochemical scheme with 60 reactions, primarily based on the recent systematic study of ion chemistry by Richards in 2011, we revised the open-source SAMI2 (Sami2 is another model of the ionosphere) model to SAMI2−ph. The scheme includes both ground state and metastable/vibrational excited compositions (e.g., N(2D), N2(ν), and O2(ν)) and associated reactions, which can remarkably affect the ionospheric electron density. The model accuracy is tested using the most widely used ionospheric data foF2 derived from mid-latitude ionosonde stations. The correlation coefficients are larger for SAMI2−ph than for SAMI2. In addition, the linear slope k is significantly closer to 1 than the default run for the NmF2 comparisons. The smaller RMSE and b indicate that the modified model provides a reasonably good match with the ionosonde NmF2 measurements. The above results demonstrate that the model with the chosen photochemical scheme performs better than the original SAMI2 at mid-latitude.

Relaxation behavior of vibrationally excited N2(X1Σg + v″ = 6) collisions with H2

Relaxation behavior of vibrationally excited N2 (X1Σg + v″ = 6) induced by collisions with H2 has been investigated using coherent anti-Stokes Raman spectroscopy (CARS). The total pressure of the N2–H2 mixture was 500 Torr, and the molar ratios of H2 were 0.3, 0.4, 0.5, 0.6 and 0.8, respectively. The v″ = 6 vibrational state of the electronic ground-state manifold X1Σg + of N2 was selectively excited by overtone pumping, and the population evolution was monitored using CARS spectroscopy. The collisional deactivation rate coefficients of the excited state N2 (v″ = 6) with H2 and N2 are approximately 2.59 × 10−14 cm3s−1 and 1.04 × 10−14 cm3s−1 at 300 K, and 2.57 × 10−14 cm3s−1 and 0.54 × 10−14 cm3s−1 at 320 K, respectively. The relaxation rate coefficient of the N2–H2 collision was approximately 2.5 and 5 times that of the self-relaxation rate coefficient. The experimental results show that the population densities of the (1,2), (2,2), (3,5), and (3,6) levels of H2 have a maximum at 320 K, while the population densities of (2,3) and (2,4) show little change with increasing temperature. Simultaneously, the time-resolved CARS profiles of the vibrational levels v = 6,5,4 by preparing v = 6 of N2 also indicated that a near-resonant multi-quantum relaxation process occurred between N2–H2. The collision-induced population distribution of H2 was observed at molar ratios of 0.3, 0.4, 0.5, 0.6 and 0.8, respectively. The ro-vibrational population distribution of H2 after collision with N2 is given by the CARS signal intensity ratio, and the population of hydrogen molecules at v = 2, 3 vibrational states also provides strong experimental evidence for energy near-resonance collisions between N2–H2.

Vibrational Kinetics of NO and N2 in the Earth's Middle Atmosphere During GLE69 on January 20, 2005

AbstractThe mechanisms of the production of vibrationally excited NO and N2 molecules at the altitudes of the middle atmosphere of the Earth during high‐energetic proton precipitation on 20 January 2005 are considered. The study of vibrational populations N2(X1Σg+,v′ > 0) during high‐energetic proton precipitation has shown different principal mechanisms in the N2(X1Σg+,v′ > 0) excitation. First, the excitation by secondary electrons is principal for vibrational levels v′ = 1−10. Second, it is obtained that intramolecular electron energy transfer process in N2(A3Σu+)+N2 collisions dominates in vibrational excitation of high vibrational levels v′ = 20−30. It is shown that the chemical reaction of metastable atomic nitrogen with molecular oxygen is the main production mechanism of vibrationally excited NO(X2Π,v > 0) and of the radiation of 5.3 and 2.7 μm infrared emissions at these altitudes. The calculated intensities of the 5.3 μm emission are compared with experimental data from SABER instrument on TIMED spacecraft received at the time of the proton precipitation. The role of VV′‐processes in the radiation of 5.3 μm infrared emission is discussed.

Влияние колебательно-возбужденного молекулярного азота на инфракрасное свечение газов O3 и N2O на высотах средней атмосферы Земли

The concentrations of N2(X1g+, v' = 1) and the emission intensities of infrared bands of ozone O3 and nitrous oxide N2O are calculated at altitudes of 30–70 km of the Earth's middle atmosphere during precipitation of electrons with energies E = 2, 4, 10 MeV. It is shown that for a given relativistic electron flux of 105 e/cm2·s·ster, the concentrations of vibrationally excited molecular nitrogen N2(X1g+, v' = 1) are about 105–106 cm–3 at altitudes of 50–70 km of the middle atmosphere. The emission profiles of the infrared bands of ozone at 4.7 µm and 9,9 µm, as well as the infrared band of nitrous oxide at 4.5 µm, are calculated for precipitation of high-energy electrons with energies E = 2, 4, 10 MeV. It has been shown for the first time that vibrationally excited nitrogen N2(X1g+, v' = 1) plays an important role in changing the infrared balance of the middle atmosphere as a result of inelastic molecular collisions with O3 and N2O molecules during precipitation of high-energy electrons.

Effect of microsecond repetitively pulsed discharges on lean blow-off limit and emission of rapidly-mixed ammonia/air swirling flames

This work aims to implement an actuator integrating a swirl burner with electrodes to explore stable and low-emission combustion of ammonia/air. The cavity structure holds a plasma torch driven by low-power microsecond repetitively pulsed discharges (µRPDs) in the nozzle, which serves as a pretreatment for ammonia/air gas before it enters the combustion region. The plasma generates strong excited N2, OH, and atomic H* and O* signals, and fitting N2 spectra indicates a rotational temperature of ∼3000 K and vibrational temperature of ∼4500 K. The flame without plasma is easier to detach from the wall and operate as a cone-shaped structure in the confined quartz tube, while plasma can help attach the flame and extend the lean blow-off limit from ∼0.6 to 0.4∼0.5 in a Reynolds number range of ∼3000 to 7500. Then, optical diagnostics for OH radical and NH2* chemiluminescence are performed to enable analysis of intermediate chemistry. The NH2* signals are distributed at the edge of the OH profile in both attachment and detachment cases. Finally, flue gas analyzers are used to find an optimal lean equivalence ratio where plasma anchors a stable ammonia/air flame with a relatively low emission of approximately 200 ppm NO and zero NH3 and H2.

Toluene degradation in air/H2O DBD plasma: A reaction mechanism investigation based on detailed kinetic modeling and emission spectrum analysis

Non-thermal plasma (NTP) is emerging as an attractive method for decomposing volatile organic compounds (VOCs). In this paper, to study toluene degradation mechanism in air/H2O dielectric barrier discharge (DBD) plasma, optical emission spectrometry (OES) was employed to in-situ monitor active species in plasma, with the permanent degradation products being detected by on-line mass spectrometry under various operations. A detailed kinetic model of NTP with incorporation of non-constant electron filed and thermal effects has also been established. A toluene degradation efficiency > 82% could be achieved at P = 115 W, Cin, toluene = 1000 ppm. The relative spectrum intensity of excited OH, O, H and N2 (A3Σ+u) increased with increase of discharge power and was decreased at higher gas flowrates. Toluene degradation was mainly induced by oxidation of OH and O at afterglow stage, while part of toluene was decomposed by attack of electrons and reactive particles N2 (A3Σ+u) in discharge stage. A toluene degradation pathway has been proposed as: toluene→benzyl→benzaldehyde→benzene→phenoxy→cyclopentadiene→polycarbenes/alkynol→CO2/H2O. Benzoquinone, benzaldehyde, cyclopentadiene and cyclopentadienyl are supposed to be important intermediates for the ring-opening of toluene. Clarification of toluene degradation behaviors at discharge and afterglowing stage could provide new insights for plasma-catalytic process in future.

The altitude of green OI 557.7 nm and blue N2+ 427.8 nm aurora

Abstract. We have performed a large statistical study of the peak emission altitude of green O(1D2–1S0) (557.7 nm) and blue N2+ 1 N (427.8 nm) aurora using observations from a network of all-sky cameras stationed across northern Finland and Sweden recorded during seven winter seasons from 2000 to 2007. Both emissions were found to typically peak at about 114 km. The distribution of blue peak altitudes is more skewed than that for the green, and the mean peak emission altitudes were 114.84 ± 0.06 and 116.55 ± 0.07 km for green and blue emissions, respectively. We compare simultaneous measurements of the two emissions in combination with auroral modelling to investigate the emission production mechanisms. During low-energy electron precipitation (<∼ 4 keV), when the two emissions peak above about 110 km, it is more likely for the green emission to peak below the blue emission than vice versa, with the difference between the two heights increasing with their average. Modelling has shown that under these conditions the dominant source of O(1S), the upper state of the green line, is energy transfer from excited N2 (A3Σu+), with a rate that depends on the product of the N2 and O number densities. Since both number densities decrease with higher altitude, the production of O(1S) by energy transfer from N2 peaks at lower altitude than the N2 ionisation rate, which depends on the N2 number density only. Consequently, the green aurora peaks below the blue aurora. When the two emissions peak below about 110 km, they typically peak at very similar altitude. The dominant source of O(1S) at low altitudes must not be energy transfer from N2, since the rate of that process peaks above the N2 ionisation rate and blue emission due to quenching of the long-lived excited N2 at low altitudes. Dissociative recombination of O2+ seems most likely to be a major source at these low altitudes, but our model is unable to reproduce observations fully, suggesting there may be additional sources of O(1S) unaccounted for.

Diagnostics of Air Purification Plasma Device by Spatially Resolved Emission Spectroscopy

A non-thermal plasma, air purification device (PlasmaShield®, MD250, Keswick, SA, Australia), was investigated using spatially resolved optical emission spectroscopy. The emission spectra were measured with two spatial dimensions to analyze and identify the transition lines of excited NO–γ (A2Σ–X2Π), N2 (C3Π–B3Π), and N2+ (B2Σ–X2Σ) systems. The N2 emission band at 337 and 316 nm were used to determine the spatially resolved vibrational temperature of N2 molecules, TvibN2. It was found that the average N2 vibrational temperatures in the x and y directions are almost the same. Two key operating parameters, supplied power and air flow, influence the N2 vibrational temperature. The results demonstrate that applying higher supplied power increases the vibrational temperature, while changes in air flow velocity do not affect the vibrational temperature values. The phenomenological plasma temperature (PPT) was also estimated from the N2 vibrational temperature. It was observed that PlasmaShield® generates excited N2 and NO only within a narrow region around the discharge electrode tip (with peak intensity below 100 µm from the tip). The study also shows no presence of excited OH*, O*, and other radicals.

(Invited) Atmospheric Pressure Plasmas for Gas Processing : N2 Fixation and CO2 Conversion into Value-Added Compounds

Plasma-based N2 fixation into NH3 or NOx (for fertilizer applications) and plasma-based CO2 conversion into value-added compounds are gaining increasing interest [1-4]. However, for real implementation, these applications need to be further improved, in terms of conversion, energy efficiency and product formation. We perform experiments in different types of plasma reactors (i.e., gliding arc (GA) plasmas in various configurations, dielectric barrier discharges (DBDs), microwave (MW) plasmas and atmospheric pressure glow discharges (APGD)), as well as plasma-liquid interactions, to investigate their performance. This is supported by computer modelling, to obtain a better insight in the underlying mechanisms.We will first provide a brief overview of the state-of-the-art in plasma-based CO2 (and CH4) conversion and N2 fixation, with different types of plasma reactors, and explain the benefits and limitations compared to other technologies. Subsequently, we will present some recent results obtained in our group. This includes experiments in the various plasma reactors, as well as modeling. We use 2D or 3D computational fluid dynamics modelling for improving the plasma reactor design. This is complemented with 0D (or quasi-1D) chemical kinetics modeling, which solves continuity equations for the various plasma species, based on production and loss terms, as defined by the chemical reactions.We will show the role of vibrationally excited CO2 or N2 levels for energy-efficient CO2 or N2 conversion, as well as the role of thermal conversion in warm plasmas (such as GA and MW plasmas) and quenching after the plasma.[1] R. Snoeckx and A. Bogaerts, Plasma technology – a novel solution for CO2 conversion ? Chem. Soc. Rev. 46, 5805-5863 (2017).[2] A. Bogaerts and E. Neyts, Plasma technology: An emerging technology for energy storage, ACS Energy Lett. 3, 1013-1027 (2018).[3] K.H.R. Rouwenhorst, Y. Engelmann, K. van ‘t Veer, R.S. Postma, A. Bogaerts and L. Lefferts, Plasma-driven catalysis: green ammonia synthesis with intermittent electricity, Green Chemistry, 22, 6258-6287 (2020).[4] K. H. R. Rouwenhorst, F. Jardali, A. Bogaerts and L. Lefferts, Plasma-based NOX synthesis: From the Birkeland-Eyde process towards energy-efficient plasma technology, Energy Envir. Sci. (2021). (DOI: 10.1039/D0EE03763J)

Numerical investigation on plasma assisted ignition of methane/air mixture excited by the synergistic nanosecond repetitive pulsed and DC discharge

Plasma assisted combustion provides possibilities for reducing ignition delays and controlling pollutant emissions. The zero-dimensional plasma and combustion models have been built up to numerically investigate the effects of the synergistic nanosecond repetitive pulsed (NRP) and DC discharge on the methane/air plasma assisted ignition. The synergistic discharge means exerting the low voltage DC discharge after the NRP discharge in one period of the discharge plasma. The simulation results indicate that the selective excitation of the vibrationally excited species N2(v), O2(v) and CH4(v) as well as the electronically excited species O2(a1Δg) and O2(b1Σg +) by the synergistic discharge is superior to that by the NRP discharge when the electron energy has been deposited into different molecular degrees of freedom. The plasma kinetic effect on the ignition enhancement is highly efficient since it can break though the threshold of the thermal effect. Both the kinetic effect and the thermal effect of the NRP discharge on ignition enhancement are relatively weaker than those of the synergistic discharge. Besides, reactions involved the N2 electronically excited species produce abundant O and H, which is conducive to the formation of the methane oxidation intermediates. e + O2 = e + O + O(1D) in the NRP discharge and e + O2 = e + O2(a1Δg) in the synergistic discharge play the crucial roles in the methane/air plasma enhance ignition, respectively.

Time resolved mechanism of the isotope selectivity in the ultrafast light induced dissociation in N2.

The time evolution of a vacuum ultraviolet excited N2 molecule is followed all the way from an ultrafast excitation to dissociation by a quantum mechanical simulation. The primary aim is to discern the role of the excitation by a pulse short compared to the vibrational period, to discern the different coupling mechanisms between different electronic states, nonadiabatic, spin orbit, and to analyze the origin of any isotopic effect. We compare the picture in the time and energy domains. The initial ultrafast excitation pumps the molecule to a coherent electronic wave packet to which several singlet bound electronic states contribute. The total nonstationary wave function is given as a coherent sum of nuclear wave packets on each electronic state times the stationary electronic wave function. When the wave packets on different electronic states overlap, they are coupled in a mass-dependent manner whether one uses an adiabatic or a diabatic electronic basis. A weak spin-orbit coupling acts as a bottleneck between the bound singlet part of phase space and the triplet manifold of states in which dissociation takes place. To describe the spin-orbit perturbation that is ongoing in time, an energy-resolved eigenstate representation appears to be more intuitive. In the eigenstate basis, the singlet-to-triplet population transfer is large only between those vibronic eigenstates that are quasiresonant in energy. The states in resonance are different for different excitation energy ranges. The resonances are mass dependent, which explains the control of the isotope effect through the profile of the pulse.

A diffuse plasma jet generated from the preexisting discharge filament at atmospheric pressure

A diffuse plasma jet was realized by expanding the preexisting argon filamentary discharge into a diffuse one at atmospheric pressure. Examination of emission spectra from the plasma jet shows that the emission intensities of OH and Ar increase with the argon flow near the quartz tube nozzle, while the N2 emission intensity first increases, then decreases, and finally approximately remains unchanged with the increase in the argon flow of interest. It is also found that with the argon flow set at 0.4 l/min, most of the reactive species are gathered close to the nozzle, the OH and Ar emission intensities decrease quickly after the plasma propagates out of the nozzle, but the N2 emission is able to propagate over a larger distance. These distinct spectral emission features of OH, N2, and Ar are attributed to the different generation and quenching mechanisms of their corresponding excited states, i.e., OH(A Σ2 +), N2(C Π3 μ), and Ar(4p)/Ar(4s) in the argon plasma jet. Additionally, the formation of the diffuse plasma jet has been clarified by observing the discharge burning phase and solving the Poisson equation for the electric field distribution in an argon cylindrical dielectric-barrier discharge. The filamentary discharge deposits charged particles onto the dielectric. The positive surface charges in the positive half cycle induce a relatively high field in the local region close to the dielectric. The relatively high field and the high pre-ionization in this local region play a key role in initiating the diffuse positive corona.

One-Step Synthesis of Silicon Oxynitride Films Using a Steady-State and High-Flux Helicon-Wave Excited Nitrogen Plasma

A steady-state and high-flux helicon-wave excited N2 plasma was used to oxynitride Si substrates for the synthesis of silicon oxynitride (SiON) films. X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS) have been extensively used to characterize surface quality of the SiON films, and it is found that a large amount of nitrogen (N) can be incorporated into the films. The result of XPS depth profiles shows that the N concentration is high near the surface and the oxide/Si interface. In the UPS spectra, absence of the reappearance of surface states suggests a resistance to clustering of the oxynitride layer. The N2 flux and Ar mixture quantity can facilitate tuning of the dissociation characteristics in N2 discharge. By modulating the N2 fractions, the N+ density reaches maximum at a N2/(N2 + Ar) flow-rate ratio of 0.5, resulting in incorporation of more N atoms into the SiON films. Considering the easy control of N2 plasma, our work opens up a new avenue for achieving high-yield SiON films at low temperature.

Morphology analysis of Escherichia coli treated with nonthermal plasma.

Nonthermal plasma agents (reactive species and charged particles) are generally generated together. Previous studies of nonthermal plasma agents did not investigate the role of a microbial inactivation agent without interference from other agents. Consequently, the exact mechanism underlying their activity remains unclear. The present experiment was conducted to study the mechanism underlying Escherichia coli inactivation by nonthermal plasma. The mechanism underlying E.coli inactivation by charged particles was studied using pure argon plasma. Results showed that cell wall damage owing to strong electrostatic forces did not occur during direct current (DC) plasma treatment with Ar or N2 . Next, the inactivation effects of excited N2∗, N2+, ozone, OH radicals, and nitric oxide were investigated using pure nitrogen plasma and air plasma. Morphological changes and cell rupture of E.coli were observed after 5min of treatment with nonthermal plasma in air, but not with argon and nitrogen plasma treatments. Our data demonstrate that reactive oxygen species play an essential role in the inactivation of E.coli. A clear understanding of the mechanisms underlying nonthermal plasma's inactivation of micro-organism is essential for the practical applications of nonthermal plasma techniques.

Single-order laser high harmonics in XUV for ultrafast photoelectron spectroscopy of molecular wavepacket dynamics

We present applications of extreme ultraviolet (XUV) single-order laser harmonics to gas-phase ultrafast photoelectron spectroscopy. Ultrashort XUV pulses at 80 nm are obtained as the 5th order harmonics of the fundamental laser at 400 nm by using Xe or Kr as the nonlinear medium and separated from other harmonic orders by using an indium foil. The single-order laser harmonics is applied for real-time probing of vibrational wavepacket dynamics of I2 molecules in the bound and dissociating low-lying electronic states and electronic-vibrational wavepacket dynamics of highly excited Rydberg N2 molecules.

Effects of the electrical parameters and gas flow rate on the generation of reactive species in liquids exposed to atmospheric pressure plasma jets

In this work, an atmospheric pressure plasma jet was fabricated and studied for plasma–liquid interactions. The plasma jet consists of a quartz-covered pin electrode and outer quartz tube with a tapered nozzle. Using the current–voltage (I-V) and optical emission characteristics of the plasma jet, the plasma density and the speed of the plume were investigated. The optical emission spectra clearly indicated the excited NO, O, OH, N2, and N2+ in the plasma plumes. Then the plasma jets were applied to the deionized water. We investigated the effects of the operating parameters such as applied voltage, pulse frequency, and gas flow rate on the generation of reactive species in the gas and liquid phases. The densities of reactive species including OH radicals were obtained at the plasma–liquid surface and inside the plasma-treated liquids using ultraviolet absorption spectroscopy and chemical probe method. The nitrite concentration was detected by Griess assay. The data are very suggestive that there is a strong correlation among the production of reactive oxygen and nitrogen species (RONS) in the plasmas and liquids.

Silicon Nitride Encapsulated Silicon Nanocrystals for Lithium Ion Batteries

Silicon nitride (SiNx) is a promising passivation material for Si nanocrystal (NC)‐based anodes in lithium‐ion batteries. We report a single‐step plasma synthesis process for growing SiNx‐encapsulated Si NCs. In this process, nucleation and growth of the Si NCs occurred in the upstream region of a continuous‐flow tubular plasma reactor via dissociation and polymerization of SiH4 diluted in Ar. The Si NC surface was nitrided downstream via N2 injection into the plasma afterglow. Infrared spectra show a N‐rich SiNx coating, with some SiSi surface bonds that remained intact with no N insertion. Photoluminescence spectra show a Si NC core with an average diameter of ∼4 nm. These SiNx‐coated Si NCs remained susceptible to oxidation in the ambient, which reduced the Si core by approximately a monolayer. Optical emission spectra from the downstream glow region show that excited N2 species likely led to surface Si nitridation.

Inelastic processes inNa+-Ne,Na+-Ar,Ne+-Na, andAr+-Na collisions in the energy range 0.5–14 keV

Absolute cross sections for charge-exchange, ionization and excitation in Na$% ^{+}-$Ne and Na$^{+}-$Ar collisions were measured in the ion energy range $% 0.5-10$ keV using a refined version of a capacitor method, and collision and optical spectroscopy methods simultaneously in the same experimental set-up. Ionization cross sections for Ne$^{+}-$Na and Ar$^{+}-$Na collisions are measured at the energies of $2-14$ keV using a crossed-beam spectroscopy method. The experimental data and the schematic correlation diagrams are used to analyze and determine the mechanisms for these processes. For the charge-exchange process in Na$^{+}$ $-$Ar collisions two nonadiabatic regions are revealed and mechanisms responsible for these regions are explained. Structural peculiarity on the excitation function for the resonance lines of argon atoms in Na$^{+}$ $-$Ar collisions are observed and the possible mechanisms of this phenomenon are explored. The measured ionization cross sections for Na$^{+}-$Ne and Ne$^{+}-$Na collisions in conjunction with the Landau-Zener formula are used to determine the coupling matrix element and transition probability in a region of pseudo-crossing of the potential curves.

Time-resolved line emission spectroscopy and the electrical currents in the plasma jet generated by dielectric barrier discharge for soft ionization

The spatially and temporally resolved optical emission from the helium capillary dielectric barrier discharge driven by a square wave high voltage was measured simultaneously with the discharge currents during the positive and negative voltage periods. The He and N2+ emission intensities were monitored at 501nm and 391nm, respectively. The plasma jet was found to be formed only during the positive voltage period, and it preceded the discharge ignition in the capillary. Thus, the measurements of the difference between the capillary discharge currents during the positive and negative voltage periods enabled quantification of the charge, which was transported through the plasma jet. The analysis of the spatiotemporal behavior of the He emission intensities in the plasma jet yielded the velocity of the helium excitation propagation and the effective plasma jet length. The combination of these measurements enabled determination of the absolute values of the plasma jet currents. The linear relationship between the He emission intensities in the plasma jet and the plasma jet currents was found to exist over the emission intensity range of two orders of magnitude. The N2+ emission intensity was also found to be linearly dependent on the plasma jet current. The fast electrons, producing the excited He atoms, were found to be located mostly within the estimated effective plasma jet length. In this region a cascade of processes involving excited He atoms, N2+ and H2O molecules lead to establishment of the conditions necessary for the plasma jet to be used as soft ionization source. The production of reactive species can be related to the plasma jet current, which can serve as a measure of the soft ionization efficiency.