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1
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Some Remarks and Calculations Concerning Collisional Fine Structure Mixing in Alkali Metal Atoms

100%
Rosiński K., Sirko L.
Acta Physica Polonica A
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1991
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vol. 79
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issue 4
543-548
EN
The analysis of all existing theoretical and experimental results concerning collisional fine structure (FS) mixing, suggesting that their agreement depends on FS separation and FS components intensity anomaly, showed that the test of the theoretical model should be made on sodium atoms. Therefore, the mixing cross sections for the nP (n = 6 ÷ 24) states of sodium atoms colliding with noble gas atoms, N2 and sodium atoms in the ground state have been calculated theoretically. Cross sections also for the lowest nP states of Na and Rb atoms have been estimated.
2
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Experimental and Numerical Studies of One-Dimensional and Three-Dimensional Chaotic Open Systems

81%
Ławniczak M., Hul O., Bauch S., Sirko L.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
749-755
EN
We present the results of experimental studies of microwave irregular networks and a three-dimensional microwave rough cavity in the presence of absorption. Microwave networks are also analyzed numerically. Microwave networks simulate one-dimensional quantum graphs. The networks consist of coaxial cables connected by joints and attenuators to control absorption. Three-dimensional microwave rough cavities have no formal analog in quantum 3D systems. However, some statistical properties of their spectra such as the level spacing distribution confirms that they belong to the wave-chaotic systems. Absorption of the cavity was changed by using a foam microwave absorber.
3
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Experimental Investigation of Reflection Coefficient and Wigner's Reaction Matrix for Microwave Graphs

81%
Hul O., Bauch S., Ławniczak M., Sirko L.
Acta Physica Polonica A
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2007
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vol. 112
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issue 4
655-664
EN
We present the results of experimental study of the distribution P(R) of the reflection coefficient R and the distributions of Wigner's reaction K matrix for irregular, tetrahedral microwave graphs (networks) in the presence of absorption. Our experimental results are in good agreement with the exact theoretical predictions of Savin et al.
4
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Isoscattering Microwave Networks - The Role of the Boundary Conditions

71%
Ławniczak M., Bauch S., Sawicki A., Kuś M., Sirko L.
Acta Physica Polonica A
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2013
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vol. 124
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issue 6
1078-1081
EN
The recent paper by Hul et al. (Phys. Rev. Lett. 109, 040402 (2012)}, see Ref. [7]) addresses an important mathematical problem whether scattering properties of wave systems are uniquely connected to their shapes? The analysis of the isoscattering microwave networks presented in this paper indicates a negative answer to this question. In this paper the sensitivity of the spectral properties of the networks to boundary conditions is tested. We show that the choice of the proper boundary conditions is extremely important in the construction of the isoscattering networks.
5
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Nodal Domains in Chaotic Microwave Rough Billiards with and without Ray-Splitting Properties

71%
Hul O., Savytskyy N., Tymoshchuk O., Bauch S., Sirko L.
Acta Physica Polonica A
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2006
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vol. 109
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issue 1
73-87
EN
We study experimentally nodal domains of wave functions (electric field distributions) lying in the regime of Breit-Wigner ergodicity in the chaotic microwave half-circular ray-splitting rough billiard. Using the rough billiard without ray-splitting properties we also study the wave functions lying in the regime of Shnirelman ergodicity. The wave functionsΨ_N of the ray-splitting billiard were measured up to the level number N=204. In the case of the rough billiard without ray-splitting properties, the wave functions were measured up to N=435. We show that in the regime of Breit-Wigner ergodicity most of wave functions are delocalized in the n, l basis. In the regime of Shnirelman ergodicity wave functions are homogeneously distributed over the whole energy surface. For such wave functions, lying both in the regimes of Breit-Wigner and Shnirelman ergodicity, the dependence of the number of nodal domainsƝ_N on the level number N was found. We show that in the regimes of Breit-Wigner and Shnirelman ergodicity least squares fits of the experimental data reveal the numbers of nodal domains that in the asymptotic limit N→∞ coincide within the error limits with the theoretical predictionƝ_N/N≃ 0.062. Finally, we demonstrate that the signed area distributionΣ_A can be used as a useful criterion of quantum chaos.
6
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Numerical and Experimental Studies of the Elastic Enhancement Factor for 2D Open Systems

71%
Ławniczak M., Białous M., Yunko V., Bauch S., Sirko L.
Acta Physica Polonica A
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2015
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vol. 128
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issue 6
974-978
EN
We present the results of numerical and experimental studies of the elastic enhancement factor W for microwave rough and rectangular cavities simulating two-dimensional chaotic and partially chaotic quantum billiards in the presence of moderate absorption. We show that for the frequency range ν=15.0-18.5 GHz, in which the coupling between antennas and the system is strong enough, the values of W for the microwave rough cavity lie below the predictions of random matrix theory and on average above the theoretical results of V. Sokolov and O. Zhirov, Phys. Rev. E 91, 052917 (2015). We also show that for the partially chaotic rectangular billiard the enhancement factor W calculated by applying the Potter-Rosenzweig model with κ=2.8±0.5 is close to the experimental one.
7
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Experimental Determination of the Autocorrelation Function of Level Velocities for Microwave Networks Simulating Quantum Graphs

71%
Ławniczak M., Borkowska A., Hul O., Bauch S., Sirko L.
Acta Physica Polonica A
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2011
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vol. 120
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issue 6A
A-185-A-190
EN
The autocorrelation function c(x) of level velocities is studied experimentally. The measurements were performed for microwave networks simulating quantum graphs. One and two ports measurements of the scattering matrix Ŝ necessary for determining c(x) were realized for the networks possessing 5 and 6 vertices, respectively. The network with six vertices was fully connected. In the case of the networks with five vertices, additionally to the fully connected configuration, we measured the networks without the bond connecting input/output vertices. The obtained experimental results besides the autocorrelation function of level velocities, also the nearest-neighbor spacing distribution and parametric velocities distribution are compared to the predictions of random matrix theory and numerical results.
8
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Analysis of Missing Level Statistics for Microwave Networks Simulating Quantum Chaotic Graphs Without Time Reversal Symmetry - the Case of Randomly Lost Resonances

61%
Ławniczak M., Białous M., Yunko V., Bauch S., Dietz B., Sirko L.
Acta Physica Polonica A
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2017
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vol. 132
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issue 6
1672-1676
EN
We present experimental and numerical studies for level statistics in incomplete spectra obtained with microwave networks simulating quantum chaotic graphs with broken time reversal symmetry. We demonstrate that, if resonance frequencies are randomly removed from the spectra, the experimental results for the nearest-neighbor spacing distribution, the spectral rigidity and the average power spectrum are in good agreement with theoretical predictions for incomplete sequences of levels of systems with broken time reversal symmetry.
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