V Radojevic’s research while affiliated with Institut za stočarstvo, Beograd-Zemun and other places

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Publications (65)


Photon energy in a.u
Photoionization of the 2p subshell in the Ar isonuclear sequence
  • Article
  • Full-text available

September 2015

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53 Reads

Journal of Physics Conference Series

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Photoionization cross-sections and photoelectron angular distributions for Ar 2p subshell in Ar, Ar⁶⁺ and Ar⁸⁺ are calculated using the relativistic MultiConfiguration Tamm-Dancoff Approximation (MCTD) [1] that takes into account certain non-RPA correlations.

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Photoionization cross section of Xe 5s. The notation 7C and 10C denote 7-configuration and 10-configuration MCTD results respectively, and RRPA [16] and RRPA-R [15] are given for comparison; L and V denote, respectively, length and velocity forms of the dipole matrix elements, and GM denotes geometric mean. Also shown are the experimental results as solid circles [1] and open circles [17]. The vertical lines at the left indicate the various theoretical thresholds.
Photoelectron angular distribution parameter β of Xe 5s. The notation 7C and 10C denote the 7-configuration and 10-configuration MCTD results respectively, and theoretical RRPA [16], RRPA-R [15] and K-matrix [16] results are given for comparison; L and V denote, respectively, length and velocity forms of the dipole matrix elements. Also shown are the experimental results [1]. The vertical lines at the left indicate the various theoretical thresholds.
Photoionization study of Xe 5s: Ionization cross sections and photoelectron angular distributions

January 2014

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139 Reads

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9 Citations

We report studies of photoelectron angular distribution and cross-section for photoionization of xenon 5s electrons using the relativistic multiconfiguration Tamm-Dancoff (MCTD) approximation. We find that MCTD provides a significantly improved agreement with experiment, compared to some of the other relativistic many body approximations such as the relativistic random phase approximation and the relativistic random phase approximation with relaxation, over the entire photon energy region bracketing the near-threshold 5s Cooper minimum, from the 5s threshold up to about 70 eV. The MCTD results in the length form are in much better agreement with the experiment than those in the velocity form, suggesting residual correlations that must be of importance.


5s photoionization cross section of atomic Ba.
Photoelectron angular distribution asymmetry parameter β for 5s photoionization of atomic Ba.
Photoionization of the 5s subshell of Ba in the region of the second Cooper minimum: Cross sections and angular distributions

September 2013

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59 Reads

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4 Citations

The photoionization of Ba 5s in the high-energy Cooper minimum region has been investigated using the relativistic-random-phase approximation and the relativistic-random-phase approximation with relaxation. Comparison with recent experiment shows good agreement for the total cross section, but only qualitative agreement for the photoelectron angular distribution asymmetry parameter, β. The disagreement was traced to the omission of photoionization-plus-excitation channels arising from the 4d subshell.



Electron correlation effects near the photoionization threshold:The Ar isoelectronic sequence

October 2011

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23 Reads

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6 Citations

Journal of Physics B Atomic and Molecular Physics

The photoionization/photodetachment of atoms/ions of the Ar (Z = 18) isoelectronic sequence is investigated using three levels of calculation: the relativistic random phase approximation (RRPA) at various levels of truncation, RRPA with relaxation (RRPA-R) and the Tamm–Dancoff approximation (TD). The evolution of correlation and relaxation effects along the isoelectronic sequence members (Cl−, Ar, K+, Sc3+, Mn7+, Cu11+, Kr18+, Mo24+ and Cd30+) is investigated.


Effects of core correlations on the photodetachment of Cu^-

June 2011

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19 Reads

The photodetachment of anions is an excellent probe for many-electron correlation effects since the valence electron is only weakly attached to the atom. In the present study the RRPA [1] and MCTD method [2] are employed to investigate the core correlation effects on the photodetachment of Cu^- (Z=29) in the low energy region. We included the core correlations by including double excitations from the core 3d subshells besides valence electron excitations. The GRASP92 [3] package was used to obtain the MCDF wave functions. Good agreement of MCTD results with experimental data [4] in the low energy region underlines the significance of core correlation effects. Using the RRPA, we have found a slight deviation of photoelectron angular distribution asymmetry parameter b4s from 2 [5] at the Cooper minimum, within the experimental errors. [4pt] [1]. W. R. Johnson and C. D. Lin, Phys. Rev. A 20, 964 (1979). [0pt] [2]. V. Radojevic' and W. R. Johnson, Phys. Rev. A 31, 2991 (1985). [0pt] [3]. F. A. Parpia et al., Comput. Phys. Commun. 94, 249 (1996) [0pt] [4]. P. Balling et al., J. Phys. B 25, L565 (1992). [0pt] [5]. G. Aravind et al., Phys. Rev. A. 79, 043411 (2009).


Valence photodetachment of Li − and Na − using relativistic many-body techniques

May 2011

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10 Reads

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12 Citations

Physical review A, Atomic, molecular, and optical physics

The multiconfiguration Tamm-Dancoff technique (MCTD) is applied to study photodetachment of negative ions of lithium and sodium. A cusplike structure is found in the photodetachment cross section just below the first detachment-plus-excitation threshold of Li- (Li 2p), and of Na- (Na 3p), in qualitative agreement with existing theoretical and experimental results. The current work emphasizes the importance of correlation in the form of configuration interaction in the photodetachment process and demonstrates the utility of MCTD in dealing with highly correlated systems.


Relaxation effects in the photodetachment of intermediate p shells of chlorine and bromine negative ions

February 2011

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12 Reads

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4 Citations

The photodetachment cross sections and angular distribution asymmetry parameters are calculated for intermediate p shells of chlorine and bromine negative ions in the relativistic random phase approximation (RRPA) to account for relativistic effects and many electron correlations, and, additionally, in the modified RRPA (RRPA-R) to account for the relaxation of the atomic core in the photodetachment process. The results of the calculations with and without the relaxation effects are compared, and it is found that the results for cross sections with and without relaxation effects in RRPA-R and RRPA are very different close to the corresponding thresholds. An attempt is made to explain the difference between the results of RRPA and RRPA-R close to the corresponding channel thresholds.PACS Nos.: 32.80.Gc, 32.80.Fb


Figure 1. Inner shell photodetachment cross section of Na -in length (L) and velocity (V) formulations. In the left panel, XB refers to excited bound states of Na -. The MCTD results are compared with experimental (Covington et al. 2001) and other theoretical results (Ivanov and Yatsyshin 2009) in the right panel of the figure. The unlabelled vertical solid lines correspond to the thresholds for channels leading to: (i) 2p 1/2 2 2p 3/2 3 3s 2 , (ii) 2p 1/2 1 2p 3/2 4 3s 2 , (iii) 2p 1/2 2 2p 3/2 3 3p 1/2 2 , (iv) 2p 1/2 1 2p 3/2 4 3p 1/2 2 , (v) 2p 1/2 2 2p 3/2 3 3p 3/2 2 , (vi) 2p 1/2 1 2p 3/2 4 3p 3/2 2 (in order from left to right).  
Inner Shell Photodetachment Of Na Using The Multi-Configuration Tamm-Dancoff Approximation

July 2010

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48 Reads

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1 Citation

The multi-configuration Tamm-Dancoff approximation (MCTD) is used to calculate the inner shell photodetachment of the Na anion. The results reproduce a resonance peak in agreement with existing experimental and theoretical data. The current work emphasizes the importance of doing configuration interaction (CI) type calculations, and proves MCTD is an apt tool to investigate the photoionization/photodetachment process.


Variation of photoelectron angular distributions along the Ar and Ca isonuclear sequences

June 2010

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14 Reads

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6 Citations

Physical review A, Atomic, molecular, and optical physics

The dipole angular distribution asymmetry parameter, β, for photoelectrons resulting from 2p photoionization of Ar, Ar6+, and Ar8+ and Ca, Ca2+, and Ca8+ of the Ar (Z=18) and Ca (Z=20) isonuclear sequences, respectively, have been studied using the relativistic random-phase approximation over a broad range of photon energy. In the absence of relaxation, it is known that inner-shell cross sections are essentially unchanged, as a function of photon energy, upon the removal of outer-shell electrons. The present results show that this is not true for the photoelectron angular distribution asymmetry parameters, particularly near the ionization thresholds.


Citations (35)


... The Cooper minima in the average 5 Wigner delay for Xenon have also been explained to be the result of interchannel couplings, with the first Cooper minimum near 35 eV being the result of couplings with the 5 ⁄ and 5 ⁄ states and the second minimum at ~120 eV being the result of couplings with the 4 ⁄ and 4 ⁄ states [59,60]. In the case of I , we also find the same 5 Cooper minima at energies approximately equal to those of Xenon. ...

Reference:

Attosecond Time Delay Trends across the Isoelectronic Noble Gas Sequence
Photoionization study of Xe 5s: Ionization cross sections and photoelectron angular distributions

... Coming to the accuracy of the full RRPA calculations in including the important relativistic and correlation effects in predicting the photoionization parameters, several previous works have compared experimental results with that from the RRPA. In the case of noble gas atoms, the RRPA methodology has shown excellent agreement with experimental results [3,28,52]. An outstanding example is the near threshold behavior of Xe photoionization parameters, which is dominated by correlation effects. ...

Application of the relativistic local-density approximation to photoionization of the outer shells of neon, argon, krypton, and xenon
  • Citing Article
  • June 1984

Physical review A, Atomic, molecular, and optical physics

... Nevertheless, there is a shift in the thresholds in both LDA and the DF calculations. The difference in the binding energies does not pose a serious difficulty to continue, since the difference is expected to merely shift the onset of the cross-section [45,46]; however, the initial charge density affects the dynamics properties decisively. Since the relativistic effects are less dominant, the 3p 3/2 and 3p 1/2 wavefunctions are exactly similar in the case of V GASW (r c ) = 1.8 a.u. ...

Dipole and quadrupole photodetachment/photoionization studies of the Ar isoelectronic sequence

Journal of Physics Conference Series

... One of the most important manifestations of the relativistic effects is the spin-orbit splitting of the nl subshell. Important consequences of this include the splitting of spectral lines, nonzero photoionization cross-section near Cooper minima etc. [17][18][19][20]. An important leveraging of the spin-orbit interaction in the photoionization from an atomic spin-orbit doublet has been seen in experiments and is understood in terms of some electron correlation effects that were not known earlier [27][28][29]. ...

Photoionization of the 5s subshell of Ba in the region of the second Cooper minimum: Cross sections and angular distributions

... For comparison we display the RPA calculation for the whole 4d shell cross-section correlated with the 5s and 5p shells. The relativistic RPA (RRPA) calculation for the 4d shell [40] is also shown. We observe a close proximity of the RPA and HF cross sections which differ only marginally from the phase derived cross sections. ...

Photodetachment of the negative iodine ion including relaxation effects
  • Citing Article
  • July 1992

Physical review A, Atomic, molecular, and optical physics

... The splitting of the minima of the relativistic channels d + and d − may be due to the difference in compactness of these final state wavefunctions. As d − is more compact than d + , the condition for minimum is first attained for the more compact d − with increasing energy [37]. On the other hand, the results from model A do not have any such energy dependent behaviour, so it shows more or less similar behaviour as predicted using the independent particle model [36]. ...

Photoionization of the outer shells of radon and radium: Relativistic random-phase approximation for high-Z atoms
  • Citing Article
  • May 1992

Physical review A, Atomic, molecular, and optical physics

... The RRPA displays remarkable success in predicting the photoionization parameters of Xe [3,28,52]. Besides the noble gas atoms, the RRPA results agree quite well with experimental results in the cases of many closed shell atoms such as Rn [28], Zn and Cd [53], etc. In the present work, the full RRPA calculations of the Hg 6s β are compared experiment [50], and the comparison exhibits quite good agreement in the near threshold Cooper minimum region. ...

Photoionization of group-IIB elements
  • Citing Article
  • January 1982

Physical review A: General physics

... The inner-shell photodetachment of Na − , which lies below Li − in the periodic table, has been studied experimentally [19], and calculations that included many-body dynamics have been performed [20,21]. Neither of those calculations could reproduce, even qualitatively, the sharp resonance that is attributed to a multiple-electron excitation process [19]. ...

Inner Shell Photodetachment Of Na Using The Multi-Configuration Tamm-Dancoff Approximation

... This is important, since the discrepancies between earlier theory and experiment for Xe 5s photoionization in the vicinities of the Cooper minima have been attributed to the omission of certain satellite ionization-plus-excitation channels [8,12,20]. To ameliorate this omission, a method has been developed that uses an explicit multiconfiguration initialstate wavefunction to include photoionization-plus excitation, along with interchannel coupling among the final channels, known as the relativistic multiconfiguration Tamm-Dancoff (RMCTD) method [27], which has been used only in very few cases so far [12,[27][28][29][30]. To generate the relativistic initialstate multiconfiguration wavefunction, the GRASP code [31] is employed. ...

Photoionization cross section of atomic cadmium using the multi-configuration Tamm-Dancoff approximation

Journal of Physics Conference Series

... As these data are not known for atomic mercury they were derived in two different ways. The first starting point were the data for silveramalgam HgAg as reported by Fahlman and Hagstrom [16]. These values were corrected on the basis of a Born-Haber process as was shown by Johansson and Martensson [17]. ...

Photoionization calculation for 3d and 3p subshells of mercury in the decoupled relativistic random-phase approximation
  • Citing Article
  • September 1983

Physics Letters A