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1
Content available remote

Studies on Vuv Lasing with Neon-Like Aluminum Ions

100%
Rahmani B.
Acta Physica Polonica A
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1998
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vol. 93
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issue 4
631-641
EN
The collisional-radiative equilibrium model has been developed in order to investigate the population inversion on aluminum plasma. The population inversion has been established between lower 3s (^{3}P^{0}_{1},^{1}P^{0}_{1}) and upper 3p (^{3}P_{0},^{1}S_{0}) levels. The vacuum ultra-violet lasing on neon-like aluminum ions provides wavelengths of 111.9 nm, 143.2 nm, 157.3 nm. The rate of relative density population, between lower 3s ^{1}P^{0}_{1} and upper 3p ^{3}P_{0} levels, reaches its highest value of 7.16 at the electron density of 10^{19} cm^{-3}. The modified expression of optical escape factor, in the case of Doppler profile, was introduced in the calculation of opacity effect on the gain magnitudes. The resonance radiation trapping by 3d configuration alters drastically the gain values. A gain greater than 1 cm^{-1} was found between lasing levels 3s ^{3}P^{0}_{1} and 3p ^{3}P_{0}. The enhancement of gain was due to the pumping of the upper level by dielectronic recombination process from the ground state of fluorine-like and by the inner-shell ionization process from excited levels of sodium-like ions.
2
Content available remote

Cross-Sections and Transport Properties of F^{-} Ions in F_2

80%
Stojanović V., Nikitović Ž., Jovanović J., Raspopović Z.
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vol. 125
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issue 1
46-48
EN
We present the new results for the simple scattering cross-section set and proposed transport coefficients for F^{-} ions in F_2 that can be used in such models. Nanbu's theory based on thermodynamic threshold energies and separating elastic and reactive collisions is used to calculate cross-sections for binary collisions of ions with atoms and molecules. Direct MC method is applied to obtain swarm parameters at temperature of T = 300 K.
3
Content available remote

Transport Coefficients in Mixtures Ar/H_2

80%
Nikitović Ž., Stojanović V.
Acta Physica Polonica A
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2013
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vol. 123
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issue 1
73-75
EN
In this work we present electron transport coefficients for electrons in Ar/H_2 mixtures for the conditions used in plasma assisted technologies for semiconductor production i.e. in moderate to very high reduced electric field E/N (E - electric field, N - gas density). We used a two term numerical solution of the Boltzmann equation at the lowest E/N and mean energies and also Monte Carlo simulation technique at moderate and high E/N. We show that a good agreement with experimental data exists for low and moderate E/N and that based on the tests for pure H_2 and Ar we can model properly the high E/N development. Results were obtained for abundances of H_2 from 1% to 50%. Such data are required to test the sets of cross-section data which are necessary in kinetic models for this mixture and also to produce transport coefficients for fluid models. Hydrogen is used for etching of organic compounds, most importantly low k dielectrics, at the same time argon as a buffer gas is added to control the mean energy and distribution function. Besides, operation at high E/N allows the generation of fast neutrals for charging free etching on nanometer scales.
4
Content available remote

Transport Parameters of F^- Ions in BF_3

80%
Nikitović Ž., Stojanović V., Raspopović Z., Jovanović J.
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vol. 126
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issue 3
724-727
EN
In this work we presented the new results for energy dependent cross-sections and transport coefficients as a function of E/N for F^- ions in BF_3 gas. Results were obtained by using the Monte Carlo technique for cross-section set determined on the basis of the Nanbu theory. Monte Carlo method is applied to obtain swarm parameters at temperature of T=300 K.
5
Content available remote

Collisional Ionization in Lithium Vapor Excited by Nanosecond Laser Pulses

80%
Mahmoud M., El Tabal A., Nady M.
Acta Physica Polonica A
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2012
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vol. 122
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issue 1
71-77
EN
We report a theoretical study of the collisional ionization processes which occur under 2s → 2p excitation of lithium vapor excited with a nanosecond pulsed laser. The time evolution of the electron energy distribution function and the atomic ion density (Li^{+}) as well as the molecular ion density (Li^{+}_2) at different lithium vapor densities was investigated. The results show a nonlinear behavior of the energy spectra of the electrons created during the interaction of the laser with the lithium vapor. The nonlinear behavior results from superelastic collisions between the free electrons produced by collisional ionization and photoionization with Li(2p). The results also show that a competition exists between the collisional ionization and photoionization processes in producing the atomic ion and the molecular ions.
6
Content available remote

Cross-Section and Transport Parameters of Ne⁺ in CF₄

80%
Nikitović Ž., Stojanović V., Raspopović Z.
Acta Physica Polonica A
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2016
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vol. 130
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issue 6
1343-1345
EN
A cross-section set for scattering Ne⁺ ions in CF₄ is assessed by using available experimental data for charge transfer cross-sections. In this paper we present new results for the mean energy, reduced mobility and diffusion coefficients for low and moderate reduced electric fields E/N (N - gas density) and account for the non-conservative collisions. The Monte Carlo method is used to calculate transport properties of Ne⁺ ions in CF₄ at temperature of T=300 K.
7
Content available remote

Rate Coefficients of F^{-} Ions in Ar/BF_{3} Mixtures

80%
Nikitović Ž., Stojanović V., Raspopović Z.
Acta Physica Polonica A
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2015
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vol. 127
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issue 6
1634-1636
EN
Transport parameters of F^{-} ions in mixtures Ar/BF_{3} in DC fields were calculated using Monte Carlo simulation technique assuming the scattering cross-section set assembled on the basis of Nanbu's technique separating elastic from reactive collisions. In this work we present characteristic energy and rate coefficients for low and moderate reduced electric fields E/N (N - gas density) and account for the non-conservative collisions.
8
Content available remote

H⁺ Scattering in n-Butanol

80%
Nikitović Ž., Raspopović Z., Stojanović V.
Acta Physica Polonica A
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2017
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vol. 132
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issue 4
1420-1423
EN
In this paper we show predictions for the low energy cross-sections and transport properties for the H⁺ in n-butanol gas. These data are needed for modelling in numerous technologically important applications. Appropriate gas phase enthalpies of formation for the products were used to calculate scattering cross-section as a function of kinetic energy. Calculated cross-sections can be used to obtain transport parameters as a function of E/N (E - electric field, N - gas density) for H⁺ in n-butanol gas.
9
Content available remote

Modeling of Excitation by Heavy Particles in Pure H_2 Discharges at High E/N

80%
Stojanović V., Nikitović Ž.
Acta Physica Polonica A
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2012
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vol. 121
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issue 3
622-624
EN
H_{ α} emission profiles were calculated for the high E/N (electric field E to gas density N ratio) Townsend discharges in pure hydrogen. Heavy particle collisions including the fast neutrals and interactions with the cathode surface are also included. The basic data were chosen to be in accordance with those used by Phelps. Monte Carlo simulation technique employing null collision method was used to follow electrons and heavy particles between collisions with H_2 or with surface for the conditions of a high E/N. Trajectories of reaction fragments are followed after the collision until their neutralization or thermalization down to the threshold of H_{ α} excitation. We obtained spatially resolved emission profiles and the Doppler broadened line profiles for the conditions of the experiment of Petrović and Phelps. Intensity of the Doppler profile wing showing H_{ α} emission of particles emerging from the cathode direction is obtained assuming that the reflection coefficient of the fast H atoms depends on the incident angle and on energy of the incident particle.
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