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Tytuł:
Raman Scattering from Acoustic Phonons Confined in Spherical Nanoparticles
Autorzy:
Kostić, R.
Powiązania:
https://bibliotekanauki.pl/articles/1807815.pdf
Data publikacji:
2009-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.46.Df
63.22.-m
Opis:
Low-frequency Raman scattering from small spherical particles is analyzed. Frequencies of vibrational modes are calculated in elastic continuum approximation, which considers one nanoparticle as homogeneous elastic sphere. Parameters of this model are transverse $(v_T)$ and longitudinal $(v_L)$ sound velocities of material, i.e. elastic properties of bulk material. Frequencies of vibrational modes are scaled as function of mentioned bulk parameters for symmetric l=0 and quadrupolar l=2 spheroidal modes, in the case of stress-free boundary conditions. Calculated values are compared with the low-frequency Raman experimental results from literature (Ge, Si, CdS, CdSe, $CeO_2$, ...). These calculated relations can be practically used to examine nanoparticles of any bulk material. We presented also a procedure how to establish $v_L$ and $v_T$ of material from low-frequency Raman spectra and dimension d of particles.
Źródło:
Acta Physica Polonica A; 2009, 116, 1; 62-64
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stimulated Raman Scattering of Nonclassical Light by Squeezed Phonons
Autorzy:
Peřina, J.
Kárská, M.
Křepelka, J.
Powiązania:
https://bibliotekanauki.pl/articles/1887739.pdf
Data publikacji:
1991-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.50
Opis:
Quantum statistical properties are derived for stimulated Raman scattering by squeezed phonons including squeezing of vacuum fluctuations in radiation modes and sub-Poisson photon behaviour. Initial radiation can be in squeezed thermalized and/or sub-Poisson states, phonon system can also be squeezed. In particular, effects of initial phase conditions, losses, initial nonclassical behaviour and phonon squeezing are demonstrated in terms of reduced factorial moments up to the fifth order in combined photon-photon and photon-phonon modes. Also photon number distribution, quadrature variances and principał squeeze parameters are shown.
Źródło:
Acta Physica Polonica A; 1991, 79, 6; 817-828
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Resonant Phonons in Adsorbed Slabs
Autorzy:
Dobrzynski, L.
Akjouj, A.
Syla, B.
Djafari-Rouhani, B.
Powiązania:
https://bibliotekanauki.pl/articles/1892256.pdf
Data publikacji:
1992-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.60.-p
Opis:
Resonant phonons, sometimes also called leaky waves, are phonons associated with a crystal defect, a surface, an adsorbed layer and whose frequencies fall inside the bulk crystal band. Such resonant phonons were studied experimentally and theoretically before for clean surfaces and for adsorbed monolayers. We present here a study of resonant phonons associated with the adsorption of a slab of L monolayers on a substrate. With the help of a simple atomic model, we obtained a closed form expression giving the variation of the transverse phonon density of states associated with the adsorption of the slab. An application which qualitatively simulates the adsorption of L monolayers of Ge on Si shows the existence of well-defined resonant phonons within the bulk acoustic band of the substrate.
Źródło:
Acta Physica Polonica A; 1992, 81, 1; 85-90
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Structural Disorder in Quasicrystals
Autorzy:
Strzałka, R.
Bugański, I.
Śmietańska, J.
Wolny, J.
Powiązania:
https://bibliotekanauki.pl/articles/354751.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
quasicrystals
structural disorder
phonons
phasons
structure factor
Opis:
One of the challenges of modern crystallography of complex systems (complex metallic alloys, proteins, aperiodic crystals and quasicrystals) is to properly describe the disorder in these systems and discuss correctly the refinement results in terms of the structural disorder. In this paper we briefly discuss a new approach to phasons and phonons in quasicrystals and focus on the new theory of phonons in these materials. A newly derived correction factor for phonons in the form of the Bessel function is the approximated way of describing optic modes in the phonon spectra of quasicrystals. It is applied to a real decagonal quasicrystal in the Al-Cu-Rh system with 56/38 atoms per thick/thin structural unit, based on 2092 unique reflections selected from the collected diffraction data, significantly improving the refinement results. The final R-factor value is 7.24%, which is over 0.5% better result comparing to originally reported. We believe our work will open a broader discussion on the disorder in quasicrystals (and other aperiodic systems) and motivate to develop new approaches to treat the diffraction data influenced by different types of disorder in the new way.
Źródło:
Archives of Metallurgy and Materials; 2020, 65, 1; 291-294
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Scattering of Excitons by Phonons in Quantum Wells
Autorzy:
Bardyszewski, W.
Prywata, M.
Powiązania:
https://bibliotekanauki.pl/articles/1947245.pdf
Data publikacji:
1996-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.Dx
71.38.+i
72.80.Ey
Opis:
A method to describe the effects of the exciton-optical phonon interaction is presented using the cumulant expansion approximation. The functional-integral technique of coherent phonon states is used in order to justify the commonly used model Hamiltonian and generate the proper perturbation series. The influence of the mutual electron-hole screening on the polaronic effects in quantum wells is analyzed.
Źródło:
Acta Physica Polonica A; 1996, 90, 4; 715-718
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Unified Approach to Interface and Confined Bulk Optical Phonons in Quantum Wells and Superlattices
Autorzy:
Röseler, J.
Suisky, D.
Powiązania:
https://bibliotekanauki.pl/articles/1924261.pdf
Data publikacji:
1992-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.Dx
Opis:
A unified description of confined optical LO, TO and interface phonons is given on the basis of vector "ghost" fields defined in the whole space. These fields are characterized by the relations for longitudinal and transversal fields. Real displacement fields are obtained by introducing confinement conditions. Interface charges and vortices appear due to this procedure.
Źródło:
Acta Physica Polonica A; 1992, 82, 5; 919-923
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Resonant Phonons in Adsorbates
Autorzy:
Dobrzynski, L.
Djafari Rouhani, B.
Zieliński, P.
Akjouj, A.
Sylla, B.
Oumghar, E.
Powiązania:
https://bibliotekanauki.pl/articles/1943987.pdf
Data publikacji:
1996-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.35.JS
68.45.-v
Opis:
After a brief review on surface phonons, we focus on resonant phonons in adsorbed thin layers. Such resonances may in general be understood within the substrate bulk band as thin layer modes shiften and broaden by the interaction with the substrate phonons. These resonant phonons appear as well-defined peaks in the phonon density of states. Their experimental study started recently by Helium atom scattering spectroscopy. This review will end by a prospective revue done mostly after the presentation of two unpublished results. First the slab resonant phonons may almost be confined in the surface slab even for frequencies falling within the bulk phonon band, if the surface slab is separated from the substrate by a buffer layer. The other prospective unpublished result deals with a model system in which the propagating phonons reach a space point from which they can continue to propagate through two different finite in space channels before reaching again a homogeneous uniform path. Such a system exhibits some frequencies for which the transmission factor vanishes. This phenomenon is related to the resonances associated with the finite additional path offered to the propagation of the phonons.
Źródło:
Acta Physica Polonica A; 1996, 89, 2; 139-144
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phonon-Induced Thermodynamic Properties of Ultra-narrow Wires
Autorzy:
Ilić, D.
Šetrajčić, J.
Jaćimovski, S.
Powiązania:
https://bibliotekanauki.pl/articles/1029824.pdf
Data publikacji:
2018-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
Phonons
ultra-narrow wire
the Green function
thermodynamics
specific heat
Opis:
In this paper, we investigated the influence of size effect on thermodynamic properties of ultra-narrow wires with a simple cubic lattice, by means of two-time dependent Green functions method, adjusted to confined crystalline structures. Poles of Green functions, which defining phonon spectra, are found by solving the secular equation. For different boundary parameters, this problem is presented graphically. The temperature behavior of ultra-narrow wire thermal capacitance is compared to that of bulk structures. It turned out that in low-temperature region thermal capacitance of the ultra-narrow wire is notably lower than in the corresponding bulk sample. How this fact reflects the thermal, conducting and superconducting properties of materials, is discussed in the conclusion.
Źródło:
Acta Physica Polonica A; 2018, 133, 1; 57-62
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of Phonons in HgCdMnTe Using Far-Infrared Reflectivity
Autorzy:
Dudziak, E.
Bożym, J.
Pruchnik, D.
Baran, J.
Powiązania:
https://bibliotekanauki.pl/articles/1929684.pdf
Data publikacji:
1993-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.30.Fs
71.45.Gm
Opis:
The first reflectivity spectra of Hg$\text{}_{1-x-y}$Cd$\text{}_{x}$Mn$\text{}_{y}$Te with 0.03 < x < 0.1 and 0 < y < 0.05 were measured in the spectral region 700-30 cm$\text{}^{-1}$ at 300 K and 90 K. The quaternary alloys measured show three mode behaviour. The experimental results are interpreted by using a classical dynamic dielectric function model.
Źródło:
Acta Physica Polonica A; 1993, 84, 3; 595-598
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Hot Phonons in a Biased Two-Dimensional InGaAs Channel
Autorzy:
Aninkevičius, V.
Liberis, J.
Matulionis, A.
Matulionienė, I.
Powiązania:
https://bibliotekanauki.pl/articles/1818476.pdf
Data publikacji:
2005-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.Kr
72.20.Ht
Opis:
Experimental dependence of microwave noise temperature on supplied electric power is used to estimate hot-phonon number in a modulation-doped In_{0.52}Al_{0.48}As/In_{0.53}Ga_{0.47}As/In_{0.7} Ga_{0.3}As/In_{0.52}Al_{0.48}As two-dimensional electron gas channel (n_{2D}=2.3×10^{12} cm^{-2}). The nonequilibrium occupancy of the involved longitudinal optical phonon states exceeds the equilibrium one nearly twice at 2 kV/cm electric field. test
Źródło:
Acta Physica Polonica A; 2005, 107, 2; 304-309
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
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