共查询到20条相似文献,搜索用时 31 毫秒
1.
We study the temperature dependence of the radiative deactivation of triplet states of Pdand Pt-porphin molecules in n-alkane matrices in the temperature range 4.2–210 K. The nature of the thermally activated “hot” lines that are observed in
phosphorescence spectra of Pdand Pt-porphin is discussed in detail. We show that, because of the degeneracy lifting of the
triplet state T
1, 2 in the crystal field of n-alkane matrices, lines of the transitions T1 → S
0 and T
2 → S
0 are spectrally spaced and, in all cases, the T
2 state is the first state that is activated with increasing temperature. We analyze the dependences of the T
2-T
1 splitting on the chelated metal ion and the type of the matrix. The possibility of measuring cryogenic temperatures with
molecular thermometers that use the thermochromic properties of Pdand Pt-porphin in n-alkane matrices is discussed. 相似文献
2.
We have recorded the fluorescence excitation spectra of three heterocyclic compounds with a chain structure [BPO (2-phenyl-5-(4-diphenylyl)oxazole),
POPOP (1,4-di[2-(5-phenyloxazolyl)]benzene, and TOPOT (1,4-di[2-(5-n-tolyloxazolyl)]benzene] and the fluorescence spectra
of POPOP, under conditions where the molecules were cooled in an ultrasonic helium jet. A line structure is observed in the
spectra of POPOP and TOPOT; for the BPO molecules, whose configuration changes considerably during electronic excitation,
vibrational structure is apparent only in the low-frequency region of the excitation spectrum, and a diffuse spectrum is recorded
starting from ν
0
0
+ 200 cm−1. For all the compounds, in the spectra we recorded vibrations with frequencies up to 100 cm−1, arising due to the flexibility of the molecular structure. The rotational contours of the lines for the electronic and vibronic
transitions of the POPOP molecules (Trot = 10.5 K) and TOPOT molecules (Trot = 15 K) are structureless and bell-shaped. The degree of polarization of the fluorescence Pfl for the jet-cooled POPOP molecules for excitation of vibrations along the absorption band up to 2000 cm−1 above ν
0
0
is practically constant (∼8.4%) and matches Pfl for high-temperature vapors.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 6, pp. 728–734, November–December, 2006. 相似文献
3.
A. Yu. Panarin V. S. Chirvony K. I. Kholostov P.-Y. Turpin S. N. Terekhov 《Journal of Applied Spectroscopy》2009,76(2):280-287
We have optimized the procedure for preparation of nanostructured silver films on the surface of mesoporous silicon (PSi)
to use them as active substrates in surface-enhanced Raman scattering (SERS) spectroscopy. The greatest enhancement of the
SERS signal was observed for samples obtained when the silver was deposited on PSi from an aqueous AgNO3 solution with concentration 1⋅10–2 M over a 10–15 minute period. The detection limit for rhodamine 6G on SERS-active substrates prepared by the optimized procedure
was 1⋅10–10 M. The enhancement factor for the SERS signal on these surfaces was estimated as ≈2⋅108. We have shown that SERS-active substrates based on mesoporous silicon are promising for detection and study of complex organic
compounds, in particular tetrapyrrole molecules.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 2, pp. 298–306, March–April, 2009. 相似文献
4.
R. M. Vlasova N. V. Drichko B. V. Petrov V. N. Semkin E. I. Zhilyaeva R. N. Lyubovskaya I. Olejniczak A. Kobayashi H. Kobayashi 《Physics of the Solid State》2004,46(11):1985-1993
Polarized reflectance and optical conductivity spectra of single crystals of two new isostructural organic conductors based
on the BEDT-TSeF molecule, namely, the κ-(BETS)4Hg2.84Br8 superconductor (T
c
=2 K) and the κ-(BETS)4Hg3Cl8 metal, which undergoes a smooth transition to the dielectric state near 35 K, have been obtained in the spectral region 700–6500
cm−1 at temperatures of 300–15 K. At 300 K, the spectra of both compounds are nearly identical and differ from the Drude spectrum
characteristic of metals. The nature of the observed difference is discussed, and the spectra are described in terms of a
cluster approach with inclusion of electron-electron correlations in the Hubbard approximation combined with the Drude model.
The parameters of the theory were determined, including the electron transfer integrals between molecules in a cluster. The
spectra in the conducting plane of the crystals were found to be essentially anisotropic, which should be assigned to specific
features of in-plane interaction between molecules. The spectra of the superconductor and the metal become increasingly different
as the temperature is lowered. The spectra of the metal obtained for T<150 K exhibit splitting of the broad electronic maximum in the mid-IR region into two bands, which is accompanied by a splitting
of a vibronic feature deriving from electron interaction with intramolecular BETS vibrations of ν3(A
g
) symmetry. No such splitting is observed in the superconductor spectra with decreasing temperature.
__________
Translated from Fizika Tverdogo Tela, Vol. 46, No. 11, 2004, pp. 1921–1929.
Original Russian Text Copyright ? 2004 by Vlasova, Drichko, Petrov, Semkin, Zhilyaeva, Lyubovskaya, Olejniczak, A. Kobayashi,
H. Kobayashi. 相似文献
5.
We have obtained and analyzed the absorption, fluorescence, and fluorescence excitation spectra of indole vapor, N-acetyl-L-tryptophan
vapor, and 3-indole aldehyde vapor. From analysis of the dependence of the fluorescence spectrum of the free indole molecules
on the wavelength of the exciting radiation λex, it follows that emission of fluorescence occurs when the molecules undergo a transition from the one electronically excited
state 1Lb. The fluorescence spectra of the studied compounds are insignificantly different, suggesting a major role for the indole
chromophore in formation of the compounds. The absorption spectrum of N-acetyl-L-tryptophan, in which the group of atoms is
added to the indole ring through a-C-C bond, is similar to the spectrum of indole, while the spectrum of 3-indole aldehyde
is significantly different from the indole spectrum due to the effect of the C=O group conjugated with the indole ring. The
fluorescence excitation spectra are considerably different from the absorption spectra. This is associated with the strong
dependence of the quantum yield for the free molecules on λex. Qualitatively, they are mirror-symmetric to the fluorescence spectra of the stodied compounds. Analysis of the data obtained
provides a basis for assuming that in the case of free molecules of indole and its derivatives, the 1La absorption in the extreme long-wavelength region of the spectrum does not overlap 1Lb absorption.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 218–222, March–April, 2007. 相似文献
6.
V. A. Svetlichnyi M. P. Samtsov O. K. Bazyl’ O. V. Smirnov D. G. Mel’nikov A. P. Lugovskii 《Journal of Applied Spectroscopy》2007,74(4):524-532
We present results of experimental and theoretical studies of the optical characteristics of a new indotricarbocyanine dye
that is capable of effectively limiting the power of laser radiation in the visible spectral range. The spectral-luminescent
and energy characteristics of the dye molecules and their absorption spectra from the excited state with nanosecond resolution
are investigated experimentally. Quantum-chemical methods are used to calculate electronic absorption spectra from the ground
(S0 → Sn) and excited (S1 → Sn) states and to determine the nature of electronic states of the molecule and the rate constants of intramolecular photophysical
processes. The results of the theoretical research agree with experimental data. It is shown that the investigated dye has
singlet-singlet absorption at 400–600 nm. Nonlinear absorption of the dye upon excitation by radiation of the second harmonic
of a Nd:YAG laser is studied by z-scanning with an open diaphragm. The ratio of dye absorption cross sections from the excited
and ground states at 532 nm is determined in the framework of a three-level model. The results are compared with those for
previously studied compounds.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 4, pp. 473–480, July–August, 2007. 相似文献
7.
The magnetic properties of complex oxides Ln
2Mn2/3Mo4/3O7 (Ln=Sm, Gd, Tb, or Y) with a pyrochlore-type structure are studied in the temperature range 2–300 K. For all compounds in the
paramagnetic state, the temperature dependence of the magnetic susceptibility is described by a generalized Curie-Weiss law
with a temperature-independent component of ∼10−6 cm3/g and with a Weiss constant Θ<0 and |Θ|<16 K. At low temperatures (T<10–12 K), the compounds have spin-glass properties; they exhibit magnetic and temperature hysteresis and the typical dependences
of the imaginary and real parts of the dynamic magnetic susceptibility on temperature and the frequency of an ac magnetic
field in a wide range of magnetization relaxation times. The data obtained suggest that d electrons are responsible for the formation of frustrated exchange interactions in the compounds and that 4f electrons in the compounds with Sm or Tb provide strong magnetic-anisotropy effects.
__________
Translated from Fizika Tverdogo Tela, Vol. 46, No. 2, 2004, pp. 287–295.
Original Russian Text Copyright ? 2004 by Korolev, Bazuev. 相似文献
8.
We have studied photoluminescence and thermoluminescence (PL and TL) in CaGa2Se4:Eu crystals in the temperature range 77–400 K. We have established that broadband photoluminescence with maximum at 571 nm
is due to intracenter transitions 4f6 5d–4f7 (8S7/2) of the Eu2+ ions. From the temperature dependence of the intensity (log I–103/T), we determined the activation energy (E
a = 0.04 eV) for thermal quenching of photoluminescence. From the thermoluminescence spectra, we determined the trap depths:
0.31, 0.44, 0.53, 0.59 eV. The lifetime of the excited state 4f6 5d of the Eu2+ ions in the CaGa2Se4 crystal found from the luminescence decay kinetics is 3.8 μsec.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 1, pp. 112–116, January–February, 2009. 相似文献
9.
To a first approximation in perturbation theory, we have obtained expressions for the rate constants for intersystem crossings
in acceptor molecules. We show that exchange interactions between the components of the donor-acceptor pair can change the
probability of intersystem crossings for both radiative T → S0 and nonradiative S1 → T transitions. The theoretical conclusions are supported by the results of experimental studies.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 550–553, July–August, 2006. 相似文献
10.
It is shown that two-dimensional (2-D) T
1–T
2 relaxation spectra are sensitive to the changing microstructure in a model food system comprising water-in-water gelatin–agarose
gelled emulsions. This 2-D relaxation–microstructure relationship suggests that T
1–T
2 spectra have the potential of acting as “fingerprint” molecular biomarkers of microstructure in complex water-rich biological
systems and this has important future implications for in vivo magnetic resonance imaging studies of food digestion and of
the changing structure of cancerous tissue. 相似文献
11.
V. M. Egorov Yu. M. Baikov N. F. Kartenko B. T. Melekh Yu. N. Filin 《Physics of the Solid State》1998,40(11):1911-1914
Differential scanning calorimetry was used to study phase transitions (PT) in the perovskite BaCeO3. It is shown that its phase state is determined by a second-order λ transition at T
tr=520–540 K and a first-order δ transition at T
tr=600–670 K. Differences in PT parameters between ceramic and fused BaCeO3 have been established.
Fiz. Tverd. Tela (St. Petersburg) 40, 2109–2112 (November 1998) 相似文献
12.
The band structure of linear chains of fullerene molecules is calculated as a function of the intermolecular π-electron overlap integral T, which increases under increasing external pressure. Chains consisting of neutral (C60) and charged (C
60
−
) molecules are studied. It is shown that there is a sharp transition from a metal (or narrow-gap semiconductor) to an insulator
(with band gap ∼1 eV)with increasing T. The proposed model makes it possible to describe the formation of solid-carbon struc-tures, containing chains of covalently
bound fullerene molecules, with different pressure-dependent semiconductor properties.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 8, 647–650 (25 April 1997) 相似文献
13.
V. N. Lazukov P. A. Alekseev E. S. Klement’ev I. P. Sadikov N. B. Kol’chugina O. D. Chistyakov 《Journal of Experimental and Theoretical Physics》1999,88(6):1202-1207
We have studied the evolution of the inelastic neutron magnetic scattering spectra of a compound with cubic symmetry, CeInCu2, in the temperature range 10–130 K, and also their transformation with variation of the Kondo temperature T
K
due to substitution of cerium ions in the system Ce1−x
(La,Y)xInCu2 at T=10 K. It turns out that the energy of the transition between the ground state and excited state of the 4 f electrons (ΔCF) in the crystal electric field in CeInCu2 increases with growth of the population of the ground state as the temperature is reduced, with a slight change in its intensity.
Such behavior is inconsistent with the notion of classical one-ion effects of the crystal electric field. We have found that
the scale of the observed variations in the excitation spectra of the 4f electrons depends on the Kondo temperature T
K
and is insensitive to disorder in the rare-earth sublattice. Thus, despite the fact that T
K
≪ΔCF, hybridization with states in the conduction band has a substantial effect on all parameters of the excitation spectrum of
the ground multiplet of the 4f electrons at low temperatures.
Zh. éksp. Teor. Fiz. 115, 2197–2206 (June 1999)
A. A. Baikov Institute of Metallurgy 相似文献
14.
We show that for a generic C1 expanding map T of the unit circle, there is a unique equilibrium state for − log T′ that is an S–R–B measure for T, and whose statistical basin of attraction has Lebesgue measure 1. We also present some results related to the question of
whether a generic C1 expanding map preserves a σ-finite measure, absolutely continuous with respect to Lebesgue measure.
Received: 8 December 2000 / Accepted: 27 March 2001 相似文献
15.
The magnetic properties of La2−2x
Sr1+2x
Mn2O7 polycrystals (x=0.3–0.4) are studied over a broad temperature range 80–600 K. Quasi-two-dimensional manganites have a complex magnetic structure
that undergoes several transitions from one type of magnetic ordering to another. A specific feature of these manganites is
a hyperbolic dependence of inverse susceptibility in the transition region from the magnetically ordered to paramagnetic state
for T>360 K. This suggests the onset of ferrimagnetism. Electron irradiation to a fluence Φ=1×1018 electrons/cm2 is shown to have no effect on the long-range magnetic order while favoring the formation of paramagnetic polarons and of
an inhomogeneous paramagnetic state.
__________
Translated from Fizika Tverdogo Tela, Vol. 45, No. 8, 2003, pp. 1440–1445.
Original Russian Text Copyright ? 2003 by Arbuzova, Naumov, Arbuzov. 相似文献
16.
We have studied the temperature dependence of the radiative deactivation of the Pd-porphine triplet states in Shpol’skii matrices
in the temperature range 1.2–210 K. A substantial transformation of the phosphorescence spectra is observed as the temperature
increases and is due to the inclusion of thermally activated Pd-porphine states in the radiative deactivation processes. The
activation energy Ea of these Pd-porphine states is measured in matrices of n-octane and n-nonane. The splitting of the lowest quasidegenerate
triplet state ΔE(T2−T1) is determined for planar and distorted conformations of the Pd-porphine macrocycle in the n-octane matrix as 40 and 57 cm−1, respectively. The ability to use the temperature dependence of the phosphorescence properties of Pd-porphine to fabricate
molecular thermometers for the low-temperature range is analyzed.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 4, pp. 460–464, July–August, 2007. 相似文献
17.
V. N. Zavaritskii 《JETP Letters》1997,65(8):663-669
The field H*(T) for the onset of dissipation is estimated self-consistently from the results of an investigation of the transverse resistance
and current-voltage characteristics of a Bi2Sr2CaCu2O8 (BSCCO-2212) single crystal in a mixed state. It is established that H* is close to H
c1 in the interval T
c/2⩽T⩽T
c. Rapid growth of H*(T), accompanied by a transformation of the current-voltage characteristics, as the temperature decreases below ≈ 40 K attests
to the formation of a nonvanishing region of stability of an ordered state of the vortex system, possibly as a result of a
change in the effective dimensionality of the fluxoid.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 8, 629–634 (25 April 1997) 相似文献
18.
Structures of H2CN and CH2CN molecules are similar to that of H2CO molecule. The H2CO has shown anomalous absorption for its transition 111–110 at 4.8 GHz in a number of cool molecular clouds. Though the molecules H2CN and CH2CN have been identified in TMC-1 and Sgr B2 through some transitions in ortho as well as in para species, here we have investigated
the condition under which transitions 111–110 and 212–211 of these molecules may show anomalous absorption.
For the present investigation, we have calculated energy levels and radiative transition probabilities. However, we have used
scaled values for collisional rate coefficients. We found that relative values of collisional rate coefficients can produce
the required anom-alous absorption in 111–110 and 212–211 transitions in the molecules.
相似文献
19.
In most homologous series of compounds made of bent-core (BC) molecules, the B2 B1 and B6 phases occur as the chain length decreases. We have studied binary mixtures of the compound 1,3-phenylene bis[4-(3-methylbenzoyloxy)]4-n-dodecylbiphenyl 4’-carboxylate (BC12) which exhibits the B2 phase with the compound 4-biphenylyl 4’-n-undecyloxybenzoate (BO11) made of rod-like (R) molecules. We find the above sequence
of occurrence of the B phases with increasing concentration of BOH. In this paper we describe the physical origin for the
formation of these phases in both pure compounds and in the mixtures. We have also found the occurrence of the biaxial smectic
A phase when the BO11 concentration is increased to 87–95.5 mol%. We also report on another binary system composed of BC12
and 4-n-octyloxy 4’- cyanobiphenyl (8OCB) made of R molecules. This system exhibits the biaxial smectic A phase down to 30°C. Using polarized
infrared spectroscopy we find that the mutual orientation of the R and BC molecules in the SmAdb liquid crystal is such that the arrow axes of the BC molecules are along the layer normal of the partial bilayer smectic
structure formed by the rods. We also describe unusual growth patterns obtained when the nematic phase transforms to the SmAdb phase in a mixture with 24 mol% of BC12. 相似文献
20.
S. Sahling J. C. Lasjaunias R. Mélin P. Monceau G. Reményi 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(1):9-17
We have investigated the effect of the magnetic field (B) on the very
low-temperature equilibrium heat capacity ceq of the quasi-1 D organic
compound (TMTTF)2Br, characterized by a commensurate Spin Density
Wave (SDW) ground state. Below 1 K, ceq is dominated by a Schottky-like
AST-2 contribution, very sensitive to the experimental time scale,
a property that we have previously measured in numerous DW compounds. Under
applied field (in the range 0.2–7 T), the equilibrium dynamics, and hence
ceq extracted from the time constant, increases enormously. For B
≥ 2–3 T, ceq varies like B2, in agreement with a
magnetic Zeeman coupling. Another specific property, common to other
Charge/Spin density wave (DW) compounds, is the occurrence of metastable
branches in ceq, induced at very low temperature by the field exceeding
a critical value. These effects are discussed within a generalization to
SDWs in a magnetic field of the available Larkin-Ovchinnikov local model of
strong pinning. A limitation of the model when compared to experiments is
pointed out. 相似文献