共查询到20条相似文献,搜索用时 31 毫秒
1.
B. K. Kardashev V. A. Stepanov P. A. Stepanov V. M. Chernov 《Physics of the Solid State》1999,41(11):1801-1804
A study of the photoluminescence excitation spectrum in a crystal of mercury diiodide is reported. Each of the two luminescence
bands peaking at 543 and 572–575 nm investigated was found to have its own excitation spectrum. The excitation spectrum of
the 575-nm line in the long-wavelength doublet band has been observed to be sensitive to strong ultrasound vibrations and
preliminary irradiation of the sample by 590-nm light. This line is associated with radiative recombination of photocarriers
at intrinsic point defects (vacancies or iodine and mercury interstitials) located close to dislocations. The binding energy
of the photosensitive center to a dislocation was estimated from the change in the excitation spectrum.
Fiz. Tverd. Tela (St. Petersburg) 41, 1965–1968 (November 1999) 相似文献
2.
The β-binaphthylene oxide molecules studied under supersonic cooling conditions have a number of specific properties due to
their nonplanarity. Low-frequency vibrations of the molecules in the excited S1 state are higher than the frequencies for
the S0 state, and conversely the high-frequency vibrations have lower frequencies. The S0-S2 fluorescence excitation spectrum is structureless. The absence of a Q branch in the rotational contour of the line for the
purely electronic transition indicates that it is substantially broadened and shifted toward shorter wavelengths as a result
of rotational perturbations of the helical structure of the molecule. Multiplet lines in the spectra of β-binaphthylene oxide
complexes with argon, krypton, and xenon correspond to different isomeric complexes. Their bond energies are below those observed
previously for planar polycyclic molecules such as perilene, fluorene, and carbazole. The greater number of isomers with xenon
is due to strengthening of the bond in the van der Waals complex and the nonequivalence of the position of the xenon atoms
on the outside and inside of the helical molecule.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 473–477, July–August, 2006. 相似文献
3.
The radiation from relativistic particles channeled in a microscopic undulator created by applying transverse ultrasonic vibrations
to a single crystal is investigated. The results of numerical investigations are presented for real crystal undulators. The
calculations show the radiation spectra in the particle and photon energy ranges where narrowing of the spectrum occurs when
the particle energy is close to a definite threshold energy.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 6, 437–441 (25 September 1998) 相似文献
4.
New bands within the ranges of 1900–2200 and 700–1000 cm–1 have been discovered in the IR absorption spectra of crystalline alkali-earth fluorides. It is found that the defects responsible
for the high frequency bands facilitate the formation of color centers during crystal growth. These bands are presumably caused
by valence vibrations of CO molecules. The low frequency bands are attributed to molecular complexes which contain oxygen-vacancy
dipoles. 相似文献
5.
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
6.
V. I. Vettegren’ N. N. Machalaba V. B. Zharov V. B. Kulik A. V. Savitskii 《Technical Physics》2011,56(6):834-837
The mechanism of solidifying a solution of polyacrylonitrile (PAN) in dimethylsulfoxide (DMSO) into which ethylene glycol
is added is studied by the method of Raman spectroscopy. In the absence of ethylene glycol, DMSO molecules produce dipole-dipole
bonds to PAN molecules. Upon adding ethylene glycol, DMSO molecules form hydrogen bonds with it and a line at 1000 cm−1 appears in the Raman spectrum, which is assigned to the valence vibrations of S=O bonds involved in the hydrogen bonds. After
DMSO is removed, ethylene glycol molecules produce hydrogen bonds with two neighboring PAN molecules, giving rise to a band
at 2264 cm−1, which is assigned to the valence vibrations of C≡N bonds involved in these hydrogen bonds. A high-viscosity gel consisting
of PAN molecules arises in which these molecules are bonded to each other through ethylene glycol molecules. 相似文献
7.
It is shown that the anharmonicity of crystal lattice vibrations in light metals such as beryllium, can give rise to a Fermi
resonance of optical one-phonon and acoustic two-phonon vibrations. New hybridized vibrational states are formed as a result
of such a resonance interaction: biphonon and quasibiphonon vibrations and renormalized optical vibrations. Depending on the
wave vector, these vibrational states can be both damped and stationary. The corresponding dispersion equation is obtained,
whose solution made it possible to determine the spectrum of these vibrations (dispersion curves and the wave vector dependence
of the damping for damped vibrations). It is shown that ultrafast damping of optical vibrations, similar to the well-known
superradiance effect for Frenkel’ and Wannier-Mott excitons, is possible.
Fiz. Tverd. Tela (St. Petersburg) 39, 542–546 (March 1997) 相似文献
8.
S. V. Dmitriev N. N. Medvedev R. R. Mulyukov O. V. Pozhidaeva A. I. Potekaev M. D. Starostenkov 《Russian Physics Journal》2008,51(8):858-865
The possibility of existence of nonlinear localized vibrational modes in an A3B two-dimensional crystal with pairwise interatomic bonds is demonstrated. Such modes are easily realized when the difference
between masses of atoms A and B is significant and the spectrum of small-amplitude crystal vibrations has a sufficiently wide
gap. The influence of the uniform tension/compression deformation on the small-amplitude crystal vibration spectrum and on
the existence of nonlinear localized modes is investigated.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 73–79, August, 2008. 相似文献
9.
The dispersion and anisotropy of the permittivity of the liquid crystal 5CB in the solid, nematic, and isotropic phases are
investigated at frequencies ranging from 50 to 1000 MHz using discretely tunable hybrid microstrip cavities. Resonance features
which grow with increasing temperature are observed in the dielectric spectra. It is found that the section of the dispersion
which is due to oriented vibrations of the mesophase molecules covers the frequency range almost up to 300 MHz, and the resonances
found could be due to conformational vibrations of the molecules.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 4, 251–253 (25 August 1997) 相似文献
10.
E. V. Korolik R. G. Zhbankov A. A. Ivanov G. K. Il’ich N. I. Insarova V. G. Leshchenko 《Journal of Applied Spectroscopy》1998,65(6):906-910
Use of low-temperature IR spectroscopy in studies of compounds with a developed system of hydrogen bonds such as DL-serine
revealed a complete set of vibrational frequencies. The region of manifestation of stretching vibrations of OH groups involved
in the formation of strong hydrogen bonds was found. It is shown experimentally that in a crystal some of the molecules of
SL-serine exist in the nonionized form. On the basis of analysis of experimental data, frequency ranges of stretching deformation
and torsional vibrations of NH
3
+
, COO−, and OH groups were determined more accurately. It is found that in the crystals there exist molecules of DL-serine with
different spatial orientation of NH
3
+
COO−, and COH groups. It is shown that conformational diversity of molecular structures is also preserved at T=18 K.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 6, pp. 864–868, November–December, 1998. 相似文献
11.
D. G. Sannikov 《JETP Letters》1997,65(9):738-742
It is shown that the interaction of the acoustic and soft optical branches of the spectrum of normal vibrations of a crystal
via a gradient invariant of the Lifshitz-invariant type explains the characteristic temperature dependences of these branches
as the point of a transition from the initial phase into an incommensurate phase is approached. A comparison is made with
the experimental data for betaine calcium chloride dihydrate — BCCD.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 9, 707–710 (10 May 1997) 相似文献
12.
A. V. Rudakova M. S. Poretskiy I. L. Marinov A. A. Tsyganenko 《Optics and Spectroscopy》2010,109(5):708-718
The state of the surface of amorphous ice with a specific surface area of about 160 m2/g obtained by the condensation of water vapor at 77 K is studied by IR spectroscopy. As the temperature increases to 130–160
K, absorption bands of surface hydroxyl groups vanish, whereas changes in bands characteristic of hydroxyl groups in the bulk
of ice are indicative of a phase transition of ice from amorphous to the polycrystalline structure. The surface sites of amorphous
ice are characterized with low-temperature adsorption of carbon monoxide. It is shown that there are two types of CO adsorption
sites, free hydroxyl groups and oxygen atoms of surface coordinately unsaturated water molecules. Upon adsorption of nitrogen,
methane, and carbon monoxide, in addition to the perturbation of surface OH groups, reversible changes in the spectrum are
observed in the region of vibrations of bulk hydroxyls, which indicate that the strength of hydrogen bonds between water molecules
in the surface layer of icy particles increases approaching the strength of these bonds in the crystal and that the ice surface
becomes less amorphous. These results indicate that the properties of the ice surface layer substantially depend on the presence
of adsorbed molecules. 相似文献
13.
M. A. Korshunov 《Journal of Applied Spectroscopy》2008,75(6):839-842
We have obtained experimental low-frequency Raman spectra for para-dibromobenzene nanofilms of thickness ∼10 μm and ∼400 nm.
With a decrease in the film thickness, the line frequencies are lowered, the linewidths increase, additional lines become
more intense. We modeled the film structure by the molecular dynamics method and calculated the histograms of the lattice
vibrational spectra by the Dean method. We found that as the film thickness decreases, the lattice parameters increase, the
orientational disorder increases at its boundary. The structure of the studied film is similar to the structure of the para-dibromobenzene
single crystal. In order to correctly interpret the lattice vibrational spectra, we need to take into account surface vibrations
and the presence of vacancies in the structure.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 838–842, November–December, 2008. 相似文献
14.
Based on polarization measurements of the low-frequency Raman spectra of p-bromochlorobenzene and calculations of the frequency spectra of lattice vibrations by the Dean method it is shown that the
structure may contain vacancies. Their presence affects the appearance of additional lines in the low-frequency spectrum,
particularly in the vicinity of 70 cm−1, and their positions depend weakly on the orientational disorder of the molecules with respect to the para substituents. The activation energies for diffusion in a randomly disordered p-bromochlorobenzene crystal with vacancies in the structure is calculated from atom-atom potentials. It is shown that the
value of the activation energy varies along a selected direction and depends on the arrangement of the p-bromochlorobenzene molecules with respect to the para substituents, in contrast to the results for ordered p-dibromobenzene and p-dichlorobenzene.
Fiz. Tverd. Tela (St. Petersburg) 40, 1835–1838 (October 1998) 相似文献
15.
35Cl nuclear quadrupole resonance as well as quantum chemical calculations were applied to study electronic structure and molecular
dynamics of the imidazole derivative 1-(2-hydroxy-3-chloroprophyl)-2, 3-dinitro-5-methyl-imidazole. The spectra of this compound
taken at 77 and 293 K show only one line, which means that there are no physically inequivalent positions of the chlorine
atoms in the elementary cell. The line width was of about 28 kHz at 77 K and the relaxation time was about 320 ms at liquid-nitrogen
temperature and about 8 ms at room temperature. As follows from the spin-lattice relaxation time measurements performed for
the compound studied, in the range 77–200 K the libration mechanism of molecular vibrations is active, while above 200 K the
activation process related to reorientation of the CH2Cl group begins. The activation energy is 18.82 kJ/ mol. The activated process of the CH2Cl group reorientations exerts rather insignificant effect on the averaging of the electric field gradient in the vicinity
of the resonant35Cl nucleus. 相似文献
16.
T. D. Ibragimov 《Journal of Applied Spectroscopy》2009,76(5):752-755
We have studied the optical transmission of a small aluminum oxide particles – liquid crystal (4-methoxybenzylidene-4′-butylaniline)
system. We have observed that at room temperature, in the spectrum we observe a transmission band with maximum at 1896 cm–1, which is shifted toward shorter wavelengths on application of a voltage and depends on temperature. The experimental results
are explained by the optical homogeneity of the system in a narrow frequency interval when the refractive indices of the particle
material and the matrix are close, and also by reorientation of the liquid crystal molecules when a voltage is applied. 相似文献
17.
S. P. Gavva 《Journal of Applied Spectroscopy》2006,73(4):473-478
An equation has been obtained for excited vibrations with combination frequencies by modifying the equation for the normal
vibrations of the molecules, using the direct product operation and its properties for the eigenvalues and eigenvectors of
the cofactor matrices within matrix perturbation theory. From the solution of the equation, the elements of the vibrational
mode tensor are determined, for which formulas are written (in terms of projectors of the matrix of the dynamic coefficients)
that take into account their changes for excited vibrations. Using these formulas makes it possible to study the effect of
perturbations on the change in the intramolecular and spectroscopic parameters of combination vibrations of the molecules.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 421–425, July–August, 2006. 相似文献
18.
General trends in formation of the observed vibrational spectra are analyzed by calculating spectral distributions of the
absorption coefficient in the IR region for 45 molecules of different classes ignoring the electrooptical paramaters of particular
bonds and structural groups. It is shown that for many molecules, only vibrations of peripheral X-H bonds make a prevailing
contribution to the total integral absorption in a wide spectral range. The effect of increasing intensities of some bands
is clearly observed for skeleton vibrations, when optical parameters of external X-H bonds are zero.
V. I. Vernadski Institute of Geochemistry and Analytical Chemistry of the Russian Academy of Sciences, 19, Kosygin St., Moscow,
117975, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 4, pp. 491–496, July–August, 1998. 相似文献
19.
An analysis of the complex absorption profile of hydrargillite in the region of stretching vibrations of the OH bond has been
performed with the use of the method of direct fitting of the second-derivative curve. The observed profile is shown to contain
an intense broad absorption band masked by eight mutually overlapping relatively narrow bands of structural OH groups of aluminum
trihydroxide. The revealed broad absorption band is apparently due to the stretching vibrations of water molecules localized
in the trihydroxide structure and the stretching vibrations of structural OH groups interacting with them via the hydrogen
bond. An estimation of the basic spectral characteristics of the absorption bands forming the complex profile has been performed.
Translated from Zhurnal Prikladnoi Spekroskopii, Vol. 67, No. 3, pp. 306–311, May–June, 2000. 相似文献
20.
The ESR spectrum of La3Ga5SiO14 single crystals activated by chromium ions is investigated. It is shown that chromium ions are incorporated into the La3Ga5SiO14 crystal lattice in the trivalent state at laoctahedric positions. Orientations of the principal magnetic axes are determined,
and parameters of the spin Hamiltonian are estimated. The effect of disorder of the crystal structure of the matrix on line
widths and shapes of the ESR spectrum of impurity Cr3+ ions is discussed.
I. Franko L’vov State University, 50, Dragomilov St., L’vov, 290005, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii,
Vol. 65, No. 6, pp. 942–946, November–December, 1998. 相似文献