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1.
Expressions for the probabilities of l-photon transitions (for arbitrary l) between the upper valence band v and lower conduction band c at two-photon resonance on the adjacent transition between the band c and the upper conduction band c 1 are obtained by means of the S transformation of the electron-photon Hamiltonian. The effects of electron band spectrum transformation and photon reemission are taken into account. 相似文献
2.
Photoconductivity of LiYxLu1–xF4:Ce,Yb (x = 0–1) crystals is measured under one- and two-step excitation. It is established that the photoconductivity is due to intra-center transitions from excited states of Ce3+ ions. The position of the ground 4 f-state of Ce3+ ion relative to the bottom of the conduction band is determined. The choice of pumping conditions to obtain the lasing on the 5d–4f transitions of trivalent cerium in these active media is substantiated. 相似文献
3.
In the absorption spectra of the hexagonal single-crystal manganite HoMnO3 in the paramagnetic ferroelectric state, lines near 1.1 and 2.0 μm were observed associated with the transitions 5 I 8 → 5 I 6 and 5 I 8 → 5 I 7, respectively, within the 4f 10 configuration of the Ho3+ ion. At T = 80 K, to the 5 I 8 → 5 I 7 transition corresponds one band at 1.9 μm for both polarizations E ∥ c and E ⊥ c. As the temperature increases from 80 to 293 K, a low-energy band with a peak at 2.04 μm for E ⊥ c and a peak at 2.07 μm for E ∥ c arises associated with transitions from an excited Stark level of the ground 5 I 8 multiplet to the Stark levels of the 5 I 7 multiplet and with an increase in the population of the initial Stark level, the energy of which is ~100 K. 相似文献
4.
V. Ya. Aleshkin L. V. Gavrilenko 《Journal of Experimental and Theoretical Physics》2004,98(6):1174-1182
The energy spectrum of localized and resonant states of shallow donors in heterostructures GaAs/AlxGa1?xAs with quantum wells is calculated. The widths of the resonant states belonging to the second size quantization subband are determined. It is shown that the width of a resonance level is mainly determined by the interaction with optical phonons. The spectrum of impurity absorption of light due to electron transitions from the ground state of the donor to the resonant states belonging to the second size quantization subband is calculated. 相似文献
5.
E. P. Ivanova 《Optics and Spectroscopy》2007,103(5):733-740
The method of extrapolation of the parameter of a model potential for states of one electron (4f, 5s, 5p, 5d, 5f) above the core 1s 22s 22p 63s 23p 63d 104s 24p 64d 10 and one vacancy (4d 9) in the same core is applied to calculate the energy levels in the silver and rhodium isoelectronic sequences with the maximum nuclear charge Z = 86. The energy levels of Ag-and Rh-like ions were used for the calculation of the energies of resonance transitions to the ground state 1 S 0 in Pd-like ions. Good agreement between the theoretical and calculated energies of the resonance transitions in Pd-like ions indicates the reliability of the results obtained. 相似文献
6.
K. V. Ivanovskikh V. A. Pustovarov B. V. Shul’gin M. Kirm 《Physics of the Solid State》2005,47(8):1446-1449
Time-resolved excitation and emission spectra of SrF2: Er3+ upon selective excitation with synchrotron radiation in the VUV and ultrasoft x-ray ranges at T = 8 K were studied. The VUV luminescence of SrF2: Er3+ derives from high-energy interconfiguration 4f105d-4f11 transitions in the Er3+ ion. The VUV emission spectrum revealed, in addition to the 164.5-nm band (millisecond-range kinetics), a band at 146.4 nm (with a decay time of less than 600 ps). The formation of excitation spectra for the f-f and f-d transitions in the Er3+ ion is discussed. 相似文献
7.
We report a quantitative investigation of the magnetic field-temperature phase diagram by taking into account a simple phenomenological model arising out of the interplay of kinetic arrest and thermodynamic transitions in a magnetic glass Pr0.5Ca0.5Mn0.975Al0.025O3, through magnetization measurements. Such studies are necessary as kinetic arrest plays an important role in the formation of “magnetic glasses”, which has been observed in systems undergoing first order magnetic phase transitions. It has been shown that disorder in a system results in the formation kinetic arrest (H K ,T K ) band, like supercooling (H *,T *) and superheating (H **,T **) band. Quantitative proofs are given to show that (H K ,T K ) band is anticorrelated with (H *,T *) and (H **,T **) bands, while the later two are correlated among themselves. Analysis of time dependence of magnetization at different temperatures is carried out to establish the fact that the kinetic arrested state is different from the supercooled state. 相似文献
8.
V. Ya. Aleshkin D. B. Veksler V. I. Gavrilenko I. V. Erofeeva A. V. Ikonnikov D. V. Kozlov O. A. Kuznetsov 《Physics of the Solid State》2004,46(1):130-137
The submillimeter (?ω=0.5–5 meV) magnetoabsorption spectra of strained Ge/Ge1?xSix(111) multilayer heterostructures with thick Ge layers (dGe=300–850 Å, dGeSi≈200 Å, x≈0.1) are investigated at T=4.2 K upon band-gap optical excitation. It is revealed that the absorption spectra contain cyclotron resonance lines of 1L electrons localized in GeSi solid solution layers (unlike the previously studied structures with thin Ge layers as quantum wells for 3L electrons). The absorption spectra of the samples with thick Ge layers (dGe=800–850 Å) exhibit cyclotron resonance lines of holes due to transitions from the lower Landau levels in the first quantum-well subband to the Landau levels belonging to the third and fifth higher subbands. 相似文献
9.
A. A. Bykov 《JETP Letters》2008,88(1):64-68
The influence of a dc electric current I dc on the low-temperature magnetotransport of high-mobility electrons in a GaAs double quantum well with two occupied size-quantization levels has been studied. The oscillations of the resistance ρ xx , which are periodic in the inverse magnetic field, have been shown to appear in the quasitwo-dimensional system under consideration at a temperature of T = 4.2 K in magnetic fields B > 0.1 T; the oscillations are caused by isoenergetic resonance transitions of the electrons between the Landau levels of different subbands. The inversion of the oscillations with an increase in I dc has been discovered. It has been found that the observed effect is due to the electron transport in a nonlinear regime. 相似文献
10.
A sequence of magnetocaloric anomalies occurring with the change in a magnetic field H is predicted for an open nanowire with the Rashba spin–orbit coupling and the induced superconducting pairing potential. The nature of such anomalies is due to the cascade of quantum transitions related to the successive changes in the fermion parity of the nanowire ground state with the growth of the magnetic field. It is shown that the critical Hc values fall within the parameter range corresponding to the nontrivial values of the Z2 topological invariant of the corresponding 1D band Hamiltonian characteristic of the D symmetry class. It is demonstrated that such features in the behavior of the open nanowire are retained even in the presence of Coulomb interactions. 相似文献
11.
Moletlanyi Tshipa 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(8):177
A theoretical investigation of the effects of hill-like and cup-like parabolic confiningelectric potentials on photoionization cross section (PCS) in a spherical quantum dot ispresented. The hill-like and the cup-like parabolic potentials are superimposed on aninfinite spherical square well (ISSW) potential. As the cup-like parabolic potentialintensifies, the peak of the PCS becomes redshifted for the s → ptransition, and becomes blueshifted for the p → d, d → f (andso forth) transitions. The hill-like parabolic potential, on the contrary, blueshiftspeaks of the PCS for s →p transitions, while it redshifts those oftransitions between higher states as it intensifies. Consequently, the two potentialsdiscriminate between transitions involving the ground state and those involving higherstates. 相似文献
12.
Naresh Kumar Mahalingavelar Paramasivam Jagdeep Kumar Anamika Gusain Prasanta Kumar Hota 《Journal of fluorescence》2018,28(5):1207-1216
Various electron donor and acceptor substituted (NO2, CN, Cl, H, OCH3, NH2) p-phenyl ethenyl-E- thiophenes (1–6) were synthesized and substituent dependent optical properties (dipole moment, transition dipole moment, oscillator strength, optical band gap, hyperpolarizability) were studied using Solvatochromism and Density functional theory. It is shown that thiophene acts as a weak electron donor in presence of an electron withdrawing p-phenyl substituent (NO2, CN, Cl), whereas thiophene acts as a weak electron acceptor in presence of an electron donating p-phenyl substituent (OCH3, NH2). In comparison to ethenyl thiophene 4, the HOMO-LUMO energy band gap is decreased upon increasing the electron donating or electron withdrawing capacity of p-phenyl substituent. From the excited state dipole moment calculation, it is shown that the excited state is highly dipolar for nitro and amino compounds 1 and 6, whereas compounds 2–5 show a non-polar excited state. As compared to the ethenyl thiophene 4, the first hyperpolarizability (β) increases upon substitution either with a strong electron withdrawing or strong electron donating p-phenyl substituent. A large β value is found for p-nitro phenyl ethenyl-E-thiophene and p-amino phenyl ethenyl-E- thiophene. Overall, these studies provide useful information in understanding the optical properties of phenyl and heterocyclic based ethenyl systems. 相似文献
13.
W. Heuer 《Zeitschrift für Physik A Hadrons and Nuclei》1966,194(3):224-233
We have investigated theL/K-capture ratio of51Cr. The values obtained for the transitions to the first excited state of51V and for both transitions to the first excited state and the ground state of51V are(N L /N K )A=0.1044±2% and (N L/NK)G=0.1033±3% respectively. They are in fairly good agreement with theoretical results which take exchange corrections into account. But there still remains a dependence of the results on the method used to obtain the capture numbers from the measured spectrum. 相似文献
14.
A. S. Kachan I. V. Kurguz I. S. Kovtunenko V. M. Mischenko 《Bulletin of the Russian Academy of Sciences: Physics》2008,72(11):1544-1547
The γ decay of the resonance-like structure observed in the 26Mg(pγ)27 Al reaction in the energy range E p = 0.8–3.0 MeV of accelerated protons has been investigated. The M1 resonance on the ground and excited states of 27Al with E* = 844 and 1014 keV is identified. The total strength of the M1 resonance on the ground state of this nucleus is determined. The position and total strength of this resonance are explained taking into account pairing forces. 相似文献
15.
A. D. Sargsyan G. T. Hakhumyan A. S. Sarkisyan A. O. Amiryan D. Sarkisyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2016,51(4):312-322
On an example of the D2-line of the Rb atoms the work of the frequency reference of atomic transitions is demonstrated, based on the application of the spectrum of a selective reflectance (SR) from the boundary of atom vapors with the use of nano-cell (NC) with the thickness L ~ λ/2, where λ is the laser wavelength equal to 780 nm. When changing the thickness of the nano-cell near the thickness L ~ λ/2, we observe the inversion of sign of the SR slope profile which is positive when L < λ/2 and negative when L > λ/2. In the case when the incidence angle of the laser beam on the surface of the nano-cell is close to the normal, in real-time it is possible to form the derivative of the SR which represents a resonance peak with ~35 MHz spectral linewidth and located at the atomic transition. The phenomenon of oscillation of the sign of slope while changing the nano-cell thickness from L ~ λ/2 up to L ~ 3/2λ is demonstrated. The practical application of the SR is noted. 相似文献
16.
A. P. Skvortsov V. A. Trepakov S. Kapphan A. Dejneka L. Jastrabik 《Physics of the Solid State》2009,51(7):1470-1472
The first results of the study of optical absorption spectra of KTaO3: Er3+ crystals are presented. In the 350–660-nm region, lines are observed deriving from intraconfigurational electronic transitions from the 4 I 15/2 ground state to levels of the 4 F 9/2, 4 S 3/2, 2 H 11/2, 4 F 7/2, 4 F 5/2(4 F 3/2), 2 G 9/2, and 4 G 11/2 excited states of the Er3+ ions. A comprehensive study of transitions to the 4 F 9/2, 4 S 3/2, 2 H 11/2, and 4 F 7/2 levels at 77 K is carried out. The number of lines observed for the above transitions fits the theoretically possible number for ?-? electronic transitions in Er3+ ions in the cubic crystal field. In the case of a differently charged substituted ion, this situation occurs only under nonlocal impurity charge compensation. The energies of the excited state levels for the transitions under study are determined. 相似文献
17.
A. D. Molchanova 《Physics of the Solid State》2018,60(10):1957-1965
The results of studies of the absorption spectra of nickel orthoborate Ni3(BO3)2 in the range of electronic d–d-transitions are reported. The obtained data are analyzed in the framework of the crystal field theory. The Ni2+ ions are located in two crystallographically nonequivalent positions 2a and 4f with point symmetry groups C2h and C2, respectively, surrounded by six oxygen ions forming deformed octahedra. The absorption spectra exhibit three intense bands corresponding to spin-resolved transitions from the ground state of nickel ion 3A2g (3F) to the sublevels of the 3T2g (3F), 3T1g (3F) and 3T1g (3P) triplets split by the spinorbit interaction and the rhombic component of the crystal field. At temperatures below 100 K, the spectra exhibit a thin structure, in which phonon-free lines can be distinguished. Comparison of the calculated frequencies of the zero-phonon transitions with the experimental data allows estimating parameters of the crystal field acting on the nickel ions in the 2a- and 4f-positions, as well as the parameters of electrostatic interaction between the 3d electrons and spin-orbit interaction constants. 相似文献
18.
I. I. Zasavitskii A. V. Mazurin Yu. G. Selivanov H. Zogg A. V. Yurushkin 《JETP Letters》2008,87(9):498-501
Two types of radiative transitions were observed in the low-temperature photoluminescence spectra of Pb1?x Eu x Te (0 ≤ x ≤ 0.09) solid solutions: an intense line corresponding to the transitions from the conduction to the valence band and a series (up to 15) of narrow lines corresponding to the transitions from the hybridized conduction band to the split Eu3+ levels. The intensity of the discrete lines increases with x, and their energies (and intensities) weakly depend on the temperature. The absorption and emission of the discrete lines are caused by the 4f 7(8 S 7/2) ? 4f 6(7 F J )[L 6 ? + 5dt 2g ] transitions. 相似文献
19.
A. V. Galeeva A. I. Artamkin N. N. Mikhailov S. A. Dvoretskii S. N. Danilov L. I. Ryabova D. R. Khokhlov 《JETP Letters》2017,106(3):162-166
For the Hg1?x Cd x Te-based structures, it is shown that the transition from the direct to invertеd spectrum is accompanied by the sign change for the signals related to the terahertz photoconductivity and to the magnetophotogalvanic effect. Within the range of chemical compositions corresponding to the inverted spectrum, the photoconductivity kinetics exhibits specific features, which can result from the surface topological states. 相似文献
20.
Plastic deformation of NaCl crystals colored by irradiation with gamma rays was found to lead to the occurrence of a band in the spectrum of IR photoconductivity stimulated by F-center-exciting light. This band corresponds to photon energies lying in the range from 0.65 to 1.11 eV and higher and has two distinct peaks, at 0.74 and 0.88 eV. The position of the former peak correlates well with the spectrum of IR quenching of the photoplastic effect, which suggests that this peak is associated with a dislocation electronic level. 相似文献