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1
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Resonance Ionization Spectroscopy and its Application

100%
Kluge H.-J.
Acta Physica Polonica A
|
1994
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vol. 86
|
issue 1
159-171
EN
Resonance ionization spectroscopy and its combination with mass spectrometry offer very high sensitivity and selectivity. The application of several variants of resonance ionization mass spectroscopy to the study of nuclear ground state properties and trace analysis of radioactive isotopes in the environment is discussed as well as the inverse process, i.e. the laser induced recombination, of bare heavy ions stored at relativistic energies in storage rings.
2
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Non-Perturbative Dynamics of Atoms in Strong Lrser Fields: Adiabatic Stability of Hydrogen Atom

63%
Faisal F. H. M., Dimou L.
Acta Physica Polonica A
|
1994
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vol. 86
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issue 1
201-211
EN
Recent investigations of laser-atom interaction at high intensities have led to the discovery of several unexpected phenomena, and their studies have deepened our understanding of non-perturbative dynamics of quantum systems subjected to unusually strong radiation fields. For the analysis and interpretation of these phenomena. We have developed an ab initio non-perturbative method, the Floquet close-coupling method, and applied it to analyse the highly non-perturbative problem of adiabatic stability of hydrogen atom. Ab initio rates of ionization as a function of the laser intensity for the excited circular states as well as related non-circular states are obtained. Our quantitatively accurate results clearly show that the predictions of the previous approximate theories such as the well-known "high-frequency" theory are qualitatively similar but differ quantitatively. The analysis of the dependence of adiabatic stability on the principal quantum number, the angular momentum, as well as on the magnetic quantum number for the Rydberg states are complemented by investigations of the behavior of the ground state for frequencies below the ionization threshold. In the latter situation we found the existence of stability windows within which the ionization probability decreases with increasing intensity but outside of which the atom becomes more unstable. It is shown here that the mechanism for the occurrence of stability windows is the self-tuned anti-resonance at specific intensities.
3
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Strong-Field Phenomena in Atoms - Quasiclassical Approach

63%
Fedorov M. V.
Acta Physica Polonica A
|
1994
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vol. 86
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issue 1
235-243
EN
A quasiclassical (WKB) approach is used to construct a theory of atomic transitions induced by a strong light field. This approach is used to find the "Coulomb-Volkov" solutions of the Schrödinger equation in which both the Coulomb and light fields are taken into account. These solutions are shown to be applicable in a region of low light frequencies, low electron energies and angular momenta. The found solutions are used to describe two kinds of processes: strong-field photoionization from highly excited (Rydberg) atomic levels, and field-assisted electron-ion scattering. In the photoionization problem the strong-field complex quasi-energies of an atom are found. A problem of the strong-field stabilization of an atom, as well as the expected behavior of the ionization time in its dependence on the light field strength are discussed.
4
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Laser-Matter Interaction with Intense Short Laser Pulses

63%
Lompré L. A.
Acta Physica Polonica A
|
1994
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vol. 86
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issue 1
135-150
EN
Laser-matter interaction in rare gases (He, Ne, Ar and Xe) has been investigated using a 1 ps Nd-glass laser pulse at 1053 nm with intensities between 10^{13} to 10^{18} W/cm^{2}. Three aspects of the interaction have been studied: the creation of multiply charged ions, the energy of the ejected electron and the propagation in an underdense plasma. At the maximum laser intensity, all electrons of the outer shell are removed, except in Ne for which charge states up to 7+ are observed. Comparison of experimental data with Ammosov et al. tunneling model shows a very good agreement, indicating that ionization with a 1 ps pulse in the near infrared light mainly occurs in tunneling regime. Electrons created in a low-density medium with energies up to 5 keV have been detected. These energies are far above the energy acquired during the ionization process, indicating that at high laser intensities electron energy is governed by ponderomotive force. Finally, the study of the propagation of an intense laser pulse in an underdense plasma shows that it is not possible to obtain simultaneously high laser intensity (10^{17}-10^{18} W/cm^{2}) and high electron density (10^{19}-10^{20} cm^{-3}). Best conditions for solving this problem will be discussed.
5
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The Initial-value Problem in the Quasi-classical Theory of Strong-field Photoionization of Rydberg Atoms

63%
Tikhonova O., Fedorov M.
Acta Physica Polonica A
|
1998
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vol. 93
|
issue 1
77-85
EN
Photoionization of Rydberg atoms is considered in the quasi-classical (WKB) approach. The total nonlinear strong-field ionization rate is found and investigated. The time of ionization, as a function of a growing field-strength amplitude, is shown to approach asymptotically the Kepler period t_{k}. Interference stabilization of Rydberg atoms is confirmed to exist in the case of short pulses (shorter than the Kepler period).
6
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Three-Particle Recombination at Low Temperature: a QED Approach

63%
Bhattacharyya S., Roy A.
Acta Physica Polonica A
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2001
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vol. 100
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issue 1
23-40
EN
A theoretical study of the three-body recombination of proton and electron in presence of a spectator electron with electronic beam at near-zero temperature is presented using field theory and invariant Lorentz gauge. Contributions from the Feynman diagrams of different orders give an insight into the physics of the phenomena. Recombination rate coefficient is obtained for low lying principal quantum number n=1 to 10. At a fixed ion beam temperature (300 K) recombination rate coefficient is found to increase in general with n, having a flat and a sharp peak at quantum states 3 and 5, respectively. In absence of any other theoretical and experimental results for low temperature formation of H-atom by three-body recombination at low lying quantum states, we have presented the theoretical results of Stevefelt and group for three-body recombination of deuteron with electron along with the present results. Three-body recombination of antihydrogen in antiproton-positron plasma is expected to yield similar result as that for three-body recombination of hydrogen formation in proton-electron plasma. The necessity for experimental investigation of low temperature three-body recombination at low quantum states is stressed.
7
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Photoionization of He - a Field Theoretic Approach

63%
Bhattacharyya S., Mitra S.
Acta Physica Polonica A
|
2001
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vol. 100
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issue 4
505-516
EN
The present paper deals with the field theoretic study of single ionization cross-sectionsσ_{ph} and σ_C of helium due to photoelectric effect and the Compton scattering, respectively, by photons of energy lying between 0-12 keV. In this energy range,σ_{ph} gradually decreases with energy whileσ_C gradually increases. There is a crossover point around 6.5 keV where σ_{ph}=σ_C=10^{-24} cm^2. Near about this crossover point σ_{ph} andσ_C curves are like mirror images. The ratio σ_C/σ_{ph} lies between 0.3 to 1.5 in the energy range under consideration. The present results are compared with existing theoretical results.
8
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Examination of the Change of the Characteristic X-Rays of the Zinc in Fluorine- and Boron-Doped ZnO Thin Films

51%
Söğüt Ö., Kerli S., Cengiz E., Apaydın G.
Acta Physica Polonica A
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2018
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vol. 133
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issue 5
1124-1128
EN
In this study, K_{β}/K_{α} X-ray intensity ratios of zinc in pure zinc, undoped ZnO thin film and boron and fluorine-doped ZnO thin films have been investigated. These samples have been excited by 59.5 keV γ-rays from a ^{241}Am annular radioactive source. K X-rays emitted by the samples have been counted using an Ultra-LEGe detector with a resolution of 150 eV at 5.9 keV. The K_{β}/K_{α} X-ray intensity ratios of the doped ZnO thin films have been compared with that of the undoped ZnO thin film. The deviations between the results can be explained by delocalization and/or charge transfer phenomena causing change in valence electronic configuration of zinc.
9
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Measurement of L Shell X-Ray Production and Average L Shell Fluorescence Yields for Some Heavy Elements at 123.6 keV

51%
Apaydin G., Aylikçi V., Kaya N., Cengiz E., Tiraşoğlu E.
Acta Physica Polonica A
|
2008
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vol. 113
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issue 6
1629-1638
EN
The L_{3l}, L_{3α}, L_{3β}, L_{2β}, L_{2γ}, L_{2η}, L_{1β} and L_{1γ} X-ray production cross-sections and L shell average fluorescence yields were measured for the elements from Re to U using excitation energy of 123.6 keV. Measurements were performed using an ^{57}Co annular radioactive source and a Si(Li) detector. The theoretical values of the cross-sections were calculated using theoretically tabulated values of subshell photoionization cross-sections;the Coster-Kronig transition probabilities were based on the Dirac-Hartree-Slater theory and radiative emission rates. Experimental results were compared with the theoretically calculated values of L shell X-ray cross-sections. The present experimental results are in agreement with theoretical values.
10
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Correlation? What Correlation?

51%
Eberly J. H.
Acta Physica Polonica A
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1994
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vol. 86
|
issue 1
151-157
EN
We describe recent developments in the theory of multi-electron atoms in strong radiation fields, with particular focus on the degree of e-e correlation accompanying a laser-atom interaction.
11
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Investigation on Zinc Selenide and Copper Selenide Thin Films Produced by Chemical Bath Deposition

51%
Durdu B., Alver U., Kucukonder A., Söğüt Ö., Kavgacı M.
Acta Physica Polonica A
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2013
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vol. 124
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issue 1
41-45
EN
The zinc selenide and copper selenide thin films were deposited by chemical deposition technique on glass substrates. For both films, sodium selenosulphate was used as a selenide ion source in an alkaline solution. The X-ray diffraction patterns show that the ZnSe has a cubic structure and Cu_3Se_2 film has a tetragonal structure. The relative intensity K_ β / K_ α of zinc and copper selenide thin films has been measured by using a ^{241}Am radioisotope source (75 mCi). The obtained results were compared with the theoretical values.
12
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Content available

Electron Energy Spectra from the Strong-Field Double-Ionization of Xenon

51%
Chaloupka J., Lafon R., Rudati J., Sheehy B., Agostini P., Kulander K., DiMauro L.
Acta Physica Polonica A
|
2002
|
vol. 101
|
issue 3
337-346
EN
The electron energy spectra correlated to the strong-field double-ionization of xenon are presented at three laser intensities. The double-ionization electrons are on average more energetic than those generated from single-ionization. This difference in energy is not manifested as a simple scaling to higher electron energies, but rather as a change in the shape of the spectra. This trend is observed at all intensities. Most notably, the comparison between single- and double-ionization spectra is very similar at low and high peak laser intensities. This could imply that a sequential double-ionization process dominates at all intensities, even where the double ion yield is enhanced.
13
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Influence of Ponderomotive Potential and NonZero Initial Momentum of Ejected Electron on Transition Rate in Multiphoton Ionization

51%
Miladinović T., Petrović V., Ristić V.
Acta Physica Polonica A
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2013
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vol. 124
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issue 4
658-660
EN
The multiphoton ionization of neutral atoms irradiated by photons is an interesting topic for experimental and also theoretical examination. We study the influence of ponderomotive potential and non-zero initial momentum of ejected electrons on transition rate, and also on the generalized cross-section in the case of a multiphoton ionization process. Also, we study how the transition rate depends on the number of absorbed photons.
14
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Circularly Polarized Laser Fields, with Different Z, Including Non-Zero Initial Momentum

51%
Ristić V., Miladinović T., Stevanović J.
Acta Physica Polonica A
|
2011
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vol. 119
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issue 6
761-763
EN
In this paper, by estimating the influence of different atom charge Z to the transition rate in tunnel ionization of atoms in strong laser fields we are devoloping further the observations from our earlier work. That is in the process of tunnel ionization including non-zero momentum into calculation of the transition rate gives result in lower transition rates for ejecting electrons from atoms by low-frequency laser fields, indicating that much of the photons are engaged in transferring energy to the free electron and thus unable to contribute to the effect of ionization. This is a conclusion that needs further experimental testing, which would clarify the mechanisms of tunnel ionization.
15
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Transition Rate Dependence on the Non-Zero Initial Momentum in the ADK-Theory

51%
Ristić V., Miladinović T., Radulović M.
Acta Physica Polonica A
|
2007
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vol. 112
|
issue 5
909-914
EN
Tunneling regime, introduced by Keldysh, in the interaction of strong lasers with atoms has been now accepted as the reliable method for describing processes when low frequency lasers are involved. Yet it was always assumed that the ionized electrons are leaving the atom with zero initial momentum. Because we are interested in how non-zero momentum influences the transition probability of tunnel ionization, we obtained the exact expression for the momentum. Here the estimation of the transition probability with nonzero momentum included was conducted. Potassium atoms in the laser field whose intensity varied from 10^{13} W/cm^2 to 10^{14} W/cm^2 were studied. It seems that all energy of laser field is used for tunneling ionization process at the beginning of laser pulse - ionization probability is large. After that, with further action of laser pulse, ionization probability decreases, probably because part of laser pulse energy is used for increasing momentum of ejected electrons, leaving smaller amounts of light quanta available for ionization of remaining electrons. If laser pulse lasts long enough, then the amounts of light quanta available for ionization become larger, resulting in increase in ionization probability, now with greater starting energy of ejected electrons.
16
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U_{P}, 3U_{P}, 11U_{P}: Above-Threshold Ionization Revisited

51%
Yang B., Schafer K. J., Walker B., Kulander K. C., Dimauro L. F., Agostini P.
Acta Physica Polonica A
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1994
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vol. 86
|
issue 1
41-50
EN
Angular distributions of very high energy photoelectrons from Xe and Kr, excited by a 50 ps, 1054 um laser, are presented. In Xe strong, narrow structures 45° off the polarization axis appear on above-threshold ionization peaks within a limited energy range centered around 9U_{P}, where U_{P} is the intensity-dependent ponderomotive energy. Under the same conditions the effect is much weaker in krypton. These structures are discussed using a very simple classical model as well as sophisticated single active electron calculations and the Keldysh-Faisal-Reiss theory. We conclude these structures are the result of single-electron dynamics involving rescattering of a tunneling component of the continuum wave function.
17
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Calculating Ionization Transition Rate for Circularly Polarized Fields, Including Non-Zero Initial Momentum

51%
Ristić V., Miladinović T., Radulović M.
Acta Physica Polonica A
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2009
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vol. 116
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issue 4
504-506
EN
Potassium atoms in circularly polarized laser field whose intensity (I) varies from 2× 10^{12} W/cm^2 to 2.5× 10^{14} W/cm^2 were studied. In the case when there is zero initial momentum, transition rate (that depends only on I) exhibits standard behaviour: as I increases, so thus the rate, until it reaches its maximum value at 1.1× 10^{14} W/cm^2; after that, rate diminishes as I increases. In the case of non-zero initial momentum, transition rate (that now depends on I but additionally on initial momentum, too) exhibits following behaviour: dependence of the rate on I follows standard pattern, it rises with increase of I until it reaches its maximum, and then diminishes. But with increase of momentum, ionization rate gradually diminishes.
18
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Nonsequential Double Ionization of Atoms in Strong Laser Pulses

45%
Prauzner-Bechcicki J., Sacha K., Eckhardt B., Zakrzewski J.
Acta Physica Polonica A
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2007
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vol. 112
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issue 4
699-706
EN
It is now possible to produce laser pulses with reproducible pulse shape and controlled carrier envelope phase. It is discussed how that can be explored in double ionisation studies. To this end we solve numerically the Schrödinger equation for a limited dimensionality model which nevertheless treats electron repulsion qualitatively correctly and allows to study correlation effects due to the Coulomb repulsion.
19
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Collision Cascade and Spike Effects of X-ray Irradiation on Optoelectronic Devices

45%
Salleh S., Abdul Amir H., Kumar Tiwari A., Pien Chee F.
Acta Physica Polonica A
|
2016
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vol. 130
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issue 1
93-97
EN
Bombardment with high energy particles and photons can cause potential hazards to the electronic systems. These effects range from degradation of performance to functional failure, which can affect the operation of a system. Such failures become increasingly likely as electronic components are getting more sophisticated, while decreasing in size and tending to a larger integration. In this paper, the effects of X-ray irradiation on a plastic encapsulated infrared light emitting diode, coupled to a plastic encapsulated silicon infrared phototransistor, with both of them being electrically isolated at ON and OFF modes, are investigated. All the devices are exposed to a total dose of up to 1000 mAs. The electrical parameters of the optoelectronic devices during the radiation exposure and at post-irradiation are compared to the pre-irradiation readings. The findings show that the highest degradation occurs at low dose of exposure; beyond 100 mAs the relative decrease in collector current of the phototransistor is gradually reduced. The most remarkable feature found, is the operational dependence of the bias collector current, indicating a higher degradation for low bias forward current of the light emitting diode. The degradation induced at the forward current of the light emitting diode by X-rays irradiation is almost negligible whereas a decrease of the rate of change in current transfer ratio is significant during the X-ray irradiation. The results show that there is no significant difference between current transfer ratio of ON mode and OFF mode radiation. It is observed that the operating mode of the optoelectronic devices after exposure to 1000 mAs of X-ray irradiation contributes no major variation in the degree of damage.
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