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Tytuł:
Windowless Open Photoacoustic Helmholtz Cell
Autorzy:
Starecki, T.
Powiązania:
https://bibliotekanauki.pl/articles/1811562.pdf
Data publikacji:
2008-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.38.Zp
43.58.Kr
Opis:
A phenomenon which is usually considered as the main disadvantage of photoacoustic Helmholtz cells is photoacoustic background signal resulting from the light absorption by the cell windows. Although there are methods which reduce this background signal, e.g. light wavelength modulation or time domain filtering of the photoacoustic response from the sample, the methods are limited to particular applications, and none of them would completely remove the mentioned background signal. The paper presents design of a windowless open photoacoustic Helmholtz cell, and preliminary results of frequency response measurements of such a cell. Removal of the windows eliminated the main source of the photoacoustic background signal. Additionally, the proposed design allows for unrestricted or forced flow of the fluid filling the cell. As a result, the cell can be easily adapted for continuous, real-time photoacoustic measurements. Under proper selection of the cell dimensions, Q-factors of such open photoacoustic Helmholtz resonators are comparable to the Q-factors of corresponding closed Helmholtz cells.
Źródło:
Acta Physica Polonica A; 2008, 114, 6A; A-211-A-216
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electron-Optical Phonon Coupling in Double-Barrier Quantum Well Structure
Autorzy:
Kaczmarek, E.
Powiązania:
https://bibliotekanauki.pl/articles/1932087.pdf
Data publikacji:
1995-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.40.Gk
63.20.Kr
Opis:
The electron-LO phonon coupling constant for double-barrier quantum well structure was calculated using the Frohlich model of the electron-phonon interaction and assuming coupling of the confined electron with bulk LO phonon mode. Magnitude of the Huang-Rhys factor g and possibility of detecting of phonon replicas in the resonant tunneling current are discussed for GaAs-Al$\text{}_{x}$Ga$\text{}_{1-x}$As and CdTe based structures.
Źródło:
Acta Physica Polonica A; 1995, 87, 1; 233-236
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Linear and Hyperpolarizabilities of Spiropyran and Derivatives
Autorzy:
Sabra, M.
Powiązania:
https://bibliotekanauki.pl/articles/1808098.pdf
Data publikacji:
2009-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
31.15.A-
32.10.Dk
33.15.Kr
Opis:
The geometry of spiropyran molecule and its derivatives was found using quasi-Newton methods, Broyden-Fletcher-Goldfarb-Shanno technique. Then ab initio quantum chemical methods were applied to calculate the ground state energies of the closed and open forms of spiropyran for different basis sets. The frequency dependent linear polarizability of spiropyran and derivatives were obtained and plotted. The found absorption peaks are different for the closed and the open structures of the spiropyran molecule.
Źródło:
Acta Physica Polonica A; 2009, 115, 3; 647-652
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phonon-Assisted Excitation Transfer in Quantum Dot Molecules
Autorzy:
Rozbicki, E.
Machnikowski, P.
Powiązania:
https://bibliotekanauki.pl/articles/2047376.pdf
Data publikacji:
2007-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.Kr
73.63.Kv
Opis:
We derive a quantum-kinetic description of phonon-assisted Förster transfer between two coupled quantum dots (a quantum dot molecule). We show that the exciton state decays to the ground state of the quantum dot molecule via a combination of the Rabi rotation and exponential decay. For moderately spaced dots this process takes place on a picosecond timescale.
Źródło:
Acta Physica Polonica A; 2007, 112, 2; 197-202
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dynamical Electro-Optical Characterization of Policryps Gratings
Autorzy:
Abbate, G.
Marino, A.
Vita, F.
Powiązania:
https://bibliotekanauki.pl/articles/2035667.pdf
Data publikacji:
2003
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.70.Df
42.79.Kr
Opis:
We have studied the dynamical response at 633 and 1550 nm of a new polymer-liquid crystal composite, realized in a form of a thick grating. This composite is known as Policryps, an acronym that stands for "Polymer Liquid Crystals Polymer Slides", because it shows a sequence of polymeric sheets alternated by layers containing only liquid crystal. Policryps gratings can be electrically switched between diffracting and non-diffracting states with a good diffraction efficiency in the visible region. After optimization of their performances, including response time, in the near infrared region, they can be conveniently proposed as a key component in photonic devices for telecom applications. Our results show very interesting response times ranging from 1 to 3 ms (switching on) and from 0.1 to 0.4 ms (switching off). Furthermore, switching ON times appear to be ruled by two different physical mechanisms with characteristic times differing by one order of magnitude. A deeper insight of these mechanisms might lead to response times, all in the submillisecond range.
Źródło:
Acta Physica Polonica A; 2003, 103, 2-3; 177-186
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Light Scattering Studies of Hydration and Structural Transformations of Lysozyme
Autorzy:
Szymańska, A.
Ślósarek, G.
Powiązania:
https://bibliotekanauki.pl/articles/1489917.pdf
Data publikacji:
2012-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
87.15.kr
34.50.-s
Opis:
We have applied the method of dynamic light scattering to analyse the lysozyme-ethanol interaction. For low ethanol concentration (below 4.3% (v/v)) no chemical denaturation process is observed. When the ethanol concentration grows above the triggering concentration the hydrodynamic radius of lysozyme increases, indicating the structural changes within the protein molecule. The observed structural modifications are attributed to dehydration and preliminary tertiary structure modification of the protein molecule.
Źródło:
Acta Physica Polonica A; 2012, 121, 3; 694-698
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Parametric Phonon-Helicon Interaction in Centrosymmetric Crystals with Strain-Dependent Dielectric Constant
Autorzy:
Artemenko, O. L.
Sevruk, B. B.
Powiązania:
https://bibliotekanauki.pl/articles/1945729.pdf
Data publikacji:
1996-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.Kr
Opis:
The process of interaction between circularly polarized coherent transverse phonons and slow electrokinetic waves in the centrosymmetric crystal placed in a longitudinal magnetic field and possessing strong strain dependence of the dielectric constant caused by the electrostriction is considered. The cut-off system of equations for the process of nonlinear four-wave interaction in crystal with a quadratic electrostriction corresponding to direct energy conversion from helicon to acoustic wave is derived. The solution is sought for numerically in the vicinity of a synchronism point determined by the intersection of helicon and phonon dispersion curves at different values of semiconductor plasma parameters. The results show the possibility of effective phonon parametric amplification in semiconductor crystal with the electroinduced elastic anisotropy.
Źródło:
Acta Physica Polonica A; 1996, 90, 3; 531-539
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Size Dependent Acoustical Properties of bcc Metal
Autorzy:
Yadav, R. R.
Pandey, D. K.
Powiązania:
https://bibliotekanauki.pl/articles/2043375.pdf
Data publikacji:
2005-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.Dc
62.65.+k
63.20.Kr
Opis:
The ultrasonic attenuation is evaluated at 300 K along [100], [110], and [111] directions for the characterization of bcc metal Ta. The size of the metal is considered in nanorange. Ultrasonic velocity, Grüneisen parameter and acoustic coupling constant that depend on second and third order elastic constants are calculated for determination of ultrasonic attenuation coefficient. Second and third order elastic constants of the bcc metal Ta at nanoscale at 300 K are also calculated starting with only two basic parameters. For the information about defects at nanoscale, the dislocation drag coefficients are calculated for the metal at different size along [100] orientation. The ultrasonic attenuation increases with the size of material as the size variation of the thermal conductivity and the thermal relaxation time. There is significant increase in the attenuation up to 150 nm.
Źródło:
Acta Physica Polonica A; 2005, 107, 6; 933-946
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positronium Formation at Low Temperatures in Polymers and Other Molecular Solids
Autorzy:
Hirade, T.
Powiązania:
https://bibliotekanauki.pl/articles/2042181.pdf
Data publikacji:
2005-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
36.10.Dr
78.70.Bj
36.20.Kr
Opis:
Positronium (Ps) formation by weakly localized long-lived electrons (trapped electrons or anions) and positrons at low temperatures successfully explained the Ps formation enhancement at low temperatures observed in polymers and molecular solids. This Ps formation process is different from Ore process and spur process. The phenomena expected by this Ps formation mechanism, such as an effect due to visible light exposure, a density dependence of weakly localized electrons and the delayed Ps formation were successfully observed as the experimental evidence of this Ps formation process. Some possibilities for application of this new Ps formation were also given. One is a new idea for estimation of spin polarity of positrons. Another is the possibility of application to study the local molecular motion by observing the decay of Ps formation intensity.
Źródło:
Acta Physica Polonica A; 2005, 107, 4; 615-622
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Gd$\text{}^{3+}$ Spin-Phonon Interactions in Rare-Earth Fluoride Crystals
Autorzy:
Paradowski, M. L.
Misiak, L. E.
Powiązania:
https://bibliotekanauki.pl/articles/2035540.pdf
Data publikacji:
2002-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.Kr
76.30.Kg
Opis:
The X-band EPR study of Gd$\text{}^{3+}$-doped LaF$\text{}_{3}$, La$\text{}_{0.9}$Ce$\text{}_{0.1}$F$\text{}_{3}$, La$\text{}_{0.9}$Nd$\text{}_{0.1}$F$\text{}_{ }$3, LiYF$\text{}_{4}$ and LiY$\text{}_{0.9}$Yb$\text{}_{0.1}$F$\text{}_{4}$ single crystals in the temperature range 4.2-295 K was carried out in order to investigate the Gd$\text{}^{3+}$ spin-phonon interactions. Spin-Hamiltonian parameters are analysed in the light of the superposition model and the rotational invariance theory for phonon-induced contributions to spin-Hamiltonian parameters. The 4f$\text{}^{7}$ electron-phonon interactions can be described by the Debye model. It is suggested, from the rotational invariance mechanism for phonon-induced contributions to spin-Hamiltonian parameters, that the rotational contributions are much smaller than those from the strain. Temperature-induced distortions of the crystal field, as well as these distortions caused by the La$\text{}^{3+}$/Nd$\text{}^{3+}$ and Y$\text{}^{3+}$/Yb$\text{}^{3+}$ substitutions, influence significantly the 4f$\text{}^{7}$ electron-phonon interactions. The coupling constant K$\text{}_{2}$ of 4f$\text{}^{7}$ electrons to the whole phonon spectrum of the crystal lattice is stronger in the LaF$\text{}_{3}$, La$\text{}_{0.9}$Ce$\text{}_{0.1}$F$\text{}_{3}$, La$\text{}_{0.9}$Nd$\text{}_{0.1}$F$\text{}_{3}$ with larger temperature-induced distortion of the Gd$\text{}^{3+}$ site symmetry than in LiYF$\text{}_{4}$, LiY$\text{}_{0.9}$Yb$\text{}_{0.1}$F$\text{}_{4}$. Our results are compared with those for Gd$\text{}^{3+}$-doped RbCdF$\text{}_{3}$ and PbF$\text{}_{2}$ single crystals.
Źródło:
Acta Physica Polonica A; 2002, 102, 3; 373-384
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electro-Optical Behavior of Dye Doped Nematic Liquid Crystal
Autorzy:
Yadav, S.
Pandey, K.
Misra, A.
Manohar, R.
Powiązania:
https://bibliotekanauki.pl/articles/1505061.pdf
Data publikacji:
2011-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.70.M-
42.79.Kr
Opis:
We report electro-optical behavior of a dye doped nematic liquid crystal. The dye doped cells have shown some improvement in some parameters important for the display devices such as threshold voltage $(V_{th})$, splay elastic constant, rotational viscosity and response time. The suppression of screening effect improves the threshold voltage for the doped sample.
Źródło:
Acta Physica Polonica A; 2011, 119, 6; 824-828
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Collective Encoding of Quantum Information in a Quantum Dot Register
Autorzy:
Grodecka, A.
Machnikowski, P.
Powiązania:
https://bibliotekanauki.pl/articles/2046914.pdf
Data publikacji:
2006-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
63.20.Kr
03.67.Pp
Opis:
We define the collective logical quantum bit as a state on an array of 2, 4, and 8 quantum dots. We show that such an array can be controlled with less phonon-induced pure dephasing than a single dot. We calculate the dephasing accompanying a single-qubit operation on the collective logical qubit by means of perturbative method describing the open system evolution under arbitrary driving.
Źródło:
Acta Physica Polonica A; 2006, 110, 2; 195-200
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
Tytuł:
Group Birefringence Measurement in Photonic Liquid Crystal Fibers by Use of Narrowband Light Sources
Autorzy:
Budaszewski, D.
Domański, A.
Powiązania:
https://bibliotekanauki.pl/articles/1795790.pdf
Data publikacji:
2009-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.79.Kr
42.25.Bs
Opis:
In the paper we present the results of investigating the effective group birefringence of photonic crystal fiber, partially infiltrated with 6CHBT liquid crystal mixture, which is a chemical abbreviation for 4-(trans-4-n-hexylcyclohexyl)isothiocyanatobenzene. We also introduce a novel method of group birefringence measurement based on phenomenon of depolarization of partially coherent light in birefringent media. We use Mueller-Stokes matrix formalism extended by additional depolarization matrix, which gives us possibility to calculate degree of polarization fluctuations of the light propagating in the liquid-crystal infiltrated microstructured optical fibres. We conducted the research for green and red semiconductor laser diodes. The results may contribute in construction of tunable photonic liquid crystal fibers depolarizer. Additionally, we have controlled birefringence of the photonic liquid crystal fibers by external electric field. These research may lead to designing a new type of fiber optic depolarizer based on photonic liquid crystal fibers.
Źródło:
Acta Physica Polonica A; 2009, 116, 3; 285-289
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Field Dependence of Phonon-Induced Drag Current of 2D Carriers
Autorzy:
Lehmann, D.
Jasiukiewicz, Cz.
Paszkiewicz, T.
Powiązania:
https://bibliotekanauki.pl/articles/1968318.pdf
Data publikacji:
1997-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.Kr
73.40.-c
Opis:
The magnetic field dependence of the drag current induced by beams of acoustic phonons is studied in a 2D gas of carriers, formed in a heterostructure. This drag current is related to the velocity of the center of mass of the gas. The elimination of the degrees of freedom related to the relative motion of the carriers leads to a Langevin equation for the center-of-mass position vector. From this equation one can obtain an expression for the induced current density which depends on carrier density-density correlation functions. An explicit formula for the time-integrated current density is derived taking into account all intra and inter Landau level transitions. Corresponding numerical results are in good agreement with the experimental patterns.
Źródło:
Acta Physica Polonica A; 1997, 92, 5; 891-894
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł

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