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1
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Absorptions and Emissions for the TmCl_6^{3-} Ion in Cs_2NaTmCl_6

100%
Acevedo R., Hurtado O., Portillo C., Stręk W.
Acta Physica Polonica A
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2001
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vol. 100
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issue 6
829-844
EN
In this work we report both experimental and theoretical studies regarding the Cs_2NaTmCl_6 elpasolite-type system, for which we have an updated database from linear and nonlinear optics. Both the absorption and the emission spectra for this system are rather complicated and a generalized vibronic crystal field-closure-ligand polarization calculation model has been employed to rationalize the observed spectral intensities. The calculation has been carried out by neglecting the interaction among the internal and the external vibrations and theoretical calculations have been performed with reference to both the emissions ^3H_4(Γ_i)>^3F_4(Γ_j) and the absorptions ^3H_6(A_1)> ^3F_4(Γ_i), ^1G_4(Γ_i), ^3H_5(Γ_l) withΓ_k (k=i,j)=A_1,E,T_1,T_2 andΓ_l=E, ^aT_1, ^bT_1,T_2. The advantages and disadvantages of our model calculation are discussed in the text, and despite the simplicity of the model it is shown that it has got some utility and flexibility to gain understanding in these complex phenomena.
2
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Analysis of Line Strength Data for the Spectra οf C(I), N(II), N(I) and O(II)

63%
Bacławski A., Musielok J.
Acta Physica Polonica A
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2009
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vol. 116
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issue 2
176-184
EN
Recently determined experimental and theoretical data on line strengths within 3s-3p and 3p-3d multiplets for C(I), N(II), N(I) and O(II) are analyzed. An overall satisfactory agreement between experimental data and results of recent sophisticated calculations is found with exception of only some weaker transitions. However, the measured and calculated relative line strengths disagree significantly with data resulting from the LS coupling scheme, particularly for 3p-3d transitions. In numerous cases these differences are - to a considerable degree - "regular" along the isoelectronic sequences C(I)-N(II) and N(I)-O(II). For some multiplets these discrepancies also correlate with departures from the Landé interval rule for terms involved in the corresponding transitions.
3
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Electron-ion Recombination at Sub-zero Temperature

63%
Bhattacharyya S., Roy A.
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vol. 95
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issue 6
911-920
EN
In this paper we have considered two-step radiative recombination channel over the existing spontaneous radiative recombination channel to explain the causes of experimentally obtained enhanced recombination rate at sub-zero temperature. The existing recombination rate due to spontaneous radiative recombination is 4 times smaller than the recent experimental data. In the case of Ne^{10+} we obtain good agreement between theory and experiment when contribution from two-step radiative recombination channel is added to the spontaneous radiative recombination channel. Recombination rate for Ar^{18+} is calculated. The radiation spectrum given out by two-step radiative recombination and spontaneous radiative recombination in the recombination rate processes are discrete spectrum and continuous spectrum, respectively. Experimental identification of these two channels through the spectral signatures is suggested.
4
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Lifetime and Collisional Depopulation Cross Section for the 14^{2}D_{3/2} State of Rb

63%
Bieniak B., Głódź M., Grzegorzewski P., Szonert J.
Acta Physica Polonica A
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1994
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vol. 85
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issue 5
813-818
EN
The lifetime τ and the cross section σ for depopulation induced by collisions with ground-state Rb atoms were measured for the 14^{2}D_{3/2} state of Rb. The experiment was performed in the gas-cell conditions in a range of Rb vapour temperatures in the vicinity of 340 K. The lifetime value τ = 1970(130) ns, agrees with the theoretical prediction with allowance for the influence of blackbody radiation as well as of the effects due to core polarizability and spin-orbit interaction. The measured cross section σ = 6.5(3.1) × 10^{-12} cm^{2} is close to the geometrical cross section. This agrees with similar observations made by other authors for the case of the lower n^{2}D states of Rb.
5
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The Emission Spectra for the Cs_2NaScCl_6:MoCl_6^{3-} System in the Fm3m Space Group

63%
Acevedo R., Meruane T., Navarro G.
Acta Physica Polonica A
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2001
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vol. 99
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issue 2
233-242
EN
On the basis of the data reported by Flint and Paulusz, we have undertaken a theoretical investigation of the intensity mechanism for the various emissions:Γ_8(^2T_{2g} ) → Γ_8(^4A_{2g}), Γ_8(^2E_{g}), Γ_8(^2T_{1g}), Γ_6(^2T_{1g}) for the Cs_2NaScCl_6:MoCl_6^{3-} system in the Fm3m-space group. The experimental data available refer to the visible and near infrared luminescence spectra of MoCl_6^{3-} complex ion in different hosts, such as Cs_2NaMCl_6 (M = Sc, Y, In), measured between 15,000 cm^{-1} and 3,000 cm^{-1} at liquid helium temperatures. At least, five luminescence transitions have been identified and assigned and each of them show extensive vibronic structure. A careful analysis of this experimental data shows that for the various observed electronic transitions, the vibrational frequencies change only slightly, and therefore there is no indication that the system undergoes both a significant and relevant Jahn-Teller distortion (along an active coordinate). There is however clear evidence that for the chloro-elpasolites, there is a strong resonance interaction between ν_3(τ_{1u} : stretching) of the MoX_6^{3-}, complex ion and that of the host when M = In, Y. Thus for M = Sc, the slighter higher host ν_3, wave number is likely to minimize the effect of this coupling. This evidence will allow us for the Cs_2NaScCl_6:MoCl_6^{3-} system to neglect, in the first-order approximation, the coupling among the internal and the external vibrations and to proceed using a both a molecular and the independent system models.
6
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Ligand-Framework Coupling Vibrations. The ^2E_g → ^4A_{2g} Transition in the Cr(CN)_6^{3-} Complex Ion

63%
Acevedo R., Passman M., Navarro G.
Acta Physica Polonica A
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2001
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vol. 99
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issue 2
215-232
EN
In this research paper we examine the role played by the bending vibrational modes of motion, δ(Cr-C-N) to influence the observed overall and relative vibronic intensity distribution for the ^2E_g → ^4A_{2g} phosphorescence of the Cr(CN)_6^{3-} complex ion. The calculation was carried out assuming both: (a) a seven-atom system model (molecular approximation) and (b) a negligible distortion from the octahedral symmetry for the system. The ligand polarization formalism was employed with reference to this system, since the ligand subsystems (CN)^{-1} are highly polarizable and as a consequence a conventional crystal field calculation would be both unrealistic and unappropriate. This system was chosen since there is a solid evidence to conclude that vibrations of the same type in the τ_{1u} and τ_{2u} symmetry blocks induce comparable intensity. This is a clear indication that both the τ_{1u} and τ_{2u}: δ(Cr-C-N) bending vibrations are exceptionally efficient to promote this radiative transition. This dynamical model is tested against the experimental data and it is shown that the model calculation, though approximate, gives results in excellent agreement with experiment.
7
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Branching Ratio Measurements for Ge I and Ge II

63%
Bratasz Ł., Musioł K.
Acta Physica Polonica A
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2000
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vol. 98
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issue 4
345-351
EN
A high resolution Fourier-transform spectrometer was used to measure branching ratios for 5s-5p, 4d-6s, 6s-6p, 5s-6p, 4d-6p, 4d-7p transitions in neutral germanium and 4d-4f, 4p^{2}-4f, 4p^{2}-5p, 5s-5p, 4p^{2}-4p, 4d-6p, 4p^{2}-6p, 4d-5f, 4p^{2}-5f, 4d-7p, 4p^{2}-7p of singly ionized germanium. Measurements were performed with a hollow cathode as a light source. Spectral lines intensities were measured in a spectral range from 200 to 3500 nm. Absolute transition probabilities for some Ge II lines were obtained using experimental lifetime values for the 4s^{2}4f^{2}F_{5/2},^{2}F_{7/2} and 4s^{2}5p^{2}P_{1/2},^{2}P_{3/2} levels. Our results for transitions in neutral germanium show that some infrared lines, so far overlooked in spectral analyses, give a strong contribution to Ge spectrum. Our transition probabilities obtained for Ge II lines are lower than all other experimental and theoretical results, in one case even by an order of magnitude.
8
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Relative Intensities of the 3d-2p Lines Emitted by Ar¹³⁺ Ions after Impact Excitation by an Electron Beam

51%
Rachedi S., Inal M.
Acta Physica Polonica A
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2016
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vol. 130
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issue 1
128-129
EN
The intensity ratio R of the dipole-allowed lines 3d²D_{3/2,5/2} → 2p²P_{3/2} and 3d²D_{3/2} → 2p²P_{1/2} emitted from highly charged boron-like Ar¹³⁺ ion collisionally excited by a monoenergetic electron beam has been theoretically studied versus electron densities from 10⁹ to 5× 10¹³ cm^{-3}. The calculations were performed at different angles θ of observation with respect to the electron beam direction and various incident-electron energies e_{ı} from 0.65 to 3 keV. By taking into account all important transitions among 290 magnetic sublevels of the 2s²2p, 2s2p², 2p³, 2s²3l, 2s2p3l, 2p²3l (l = 0-2) configurations, a collisional-radiative model has been used for determining the populations of the upper magnetic sublevels of the lines. All required atomic data were computed with the Flexible Atomic Code. We find that the effect of anisotropy in the photon emission, due to the directionality of the incident electron beam, can lead to very significant differences between R(0°) and R(90°). Our results also indicate that the contribution from the ²D_{3/2}→ ²P_{3/2} line which blends with the ²D_{5/2} → ²P_{3/2} line enhances the effect of anisotropy.
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