共查询到20条相似文献,搜索用时 62 毫秒
1.
B. H. Yanga P. C. Stancil 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(3):317-324
Quantum close-coupling and coupled-state approximation scattering calculations for rotational energy transfer of rotationally
excited CH4 due to collisions with He are presented for collision energies between 10−7 and 3000 cm−1 using the MP4 potential of Calderoni et al. [J. Chem. Phys. 121, 8261 (2004)]. State-to-state cross sections and rate coefficients
from selected initial rotational states of CH4 in symmetries A, E, and F are studied from the ultra-cold to the thermal regime. Comparison of the cross sections with available theoretical results
and experimental data show good agreement. Applications to astrophysics and cold laboratory environments are briefly addressed. 相似文献
2.
S. W. Tang L. L. Sun J. D. Feng H. Sun R. S. Wang Y. F. Chang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(2):197-204
A systematic investigation of D3 C32 fullerene and its derivatives C32Xn (X = H and Cl) has been performed using B3LYP/6-31G(d) method based on the density functional theory. The geometry structures,
reaction energies, relative stabilities, and electronic properties have been studied. By investigating the possible C32Xn (X = H and Cl) molecules, C32H2 and C32Cl2 behave more thermodynamically accessible with respect to other derivatives. The frontier molecular orbitals and electronic
density of states calculations of C32X2 system indicate that H and Cl passivation have less contribution to the electronic structures, but significantly improve
the stability of D3 C32 fullerene. Finally, the 13C NMR chemical shifts of C32H2 and C32Cl2 have been simulated to provide helpful information for further experiment identification. 相似文献
3.
Vera V. Baturo Sergey S. Lukashov Sergey A. Poretsky Anatoly M. Pravilov 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2017,71(9):227
This paper is an overview of our recent experimental investigations of the RgI2 van der Waals complexes, Rg = He, Ar, Kr, performed by means of laser induced fluorescence spectroscopy, optical-optical double resonance and supersonic molecular beam techniques. Spectroscopic parameters of these complexes in the E0 g + ion-pair state, such as binding energies and several spectroscopic constants, have been determined. Most likely, the potential energy surfaces of the all RgI2(E) complexes under study present T-shaped minima. Vibrational and electronic predissociations of the RgI2(E) complexes were analyzed. Relative contributions of the different electronic predissociation channels and vibrational distributions of the decay products were determined. Possible mechanisms of the complexes decay are suggested and discussed. 相似文献
4.
The effect of dehydration-induced structural transitions on the ferrimagnetic resonance spectra of the [Cr(CN)6][Mn(S)-pnH(H2O)](H2O) chiral molecular magnet has been studied for three crystalline modifications. The differences in the anisotropy field and
exchange interaction constants due to the change in the dimensionality of the magnetic ordering upon the phase transitions
have been established. In the dehydrated amorphous phase, apart from the ferrimagnetic resonance, additional isotropic magnetic
resonance lines corresponding to the spin-glass state have been revealed. 相似文献
5.
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
6.
N. Coluccelli G. Galzerano L. Bonelli A. Toncelli A. Di Lieto M. Tonelli P. Laporta 《Applied physics. B, Lasers and optics》2008,92(4):519-523
We present a comparative analysis on the growth, the spectroscopic features, and the cw laser action of room-temperature Yb(5%):LiYF4 (YLF) and Yb(10%):KYF4 (KYF) crystals. Optical slope efficiencies of 33% and 52% have been demonstrated for Yb:YLF and Yb:KYF crystals, respectively.
A remarkable wide wavelength tunability from 1.01 to 1.07 μm has been obtained for both laser crystals. 相似文献
7.
Relative cross sections, differential in energy and angle, for electrons ejected from CH4 and C3H8 molecules under 16.0 keV electron impact have been measured. Electrons were analyzed by a 45° parallel plate electrostatic
analyzer at emission angles varying from 60° to 135° with energies from 50 eV to 1000 eV. The angular distributions of electrons
exhibit structures which are found to arise from Coulomb and non-Coulomb interactions. Furthermore, the double differential
cross sections of electrons ejected from C3H8 molecule are found to be higher in magnitude than those from CH4. This result supports the fact that the number of ejected electrons participating in collisions with C3H8 molecules is more than that in CH4. Also, the angular distributions of C-K-shell Auger electrons emitted from the target molecules have been studied and shown
to be isotropic within the experimental uncertainty 相似文献
8.
A. A. Golovatenko M. A. Semina A. V. Rodina T. V. Shubina 《Physics of the Solid State》2018,60(8):1510-1513
In the limit of strong quantum confinement the lower energy states of excitons and biexcitons in spheroidal quantum dots of semiconductors with a fourfold degenerate vertex of the valence band, which are active in the dipole approximation at one- and two-photon excitation, have been considered. The comparative analysis of the order of energy levels of the hole in the potentials of the infinitely deep quantum well and a three-dimensional harmonic oscillator taking into account the axial anisotropy of the quantum dot (QD) shape is carried out. It is shown that the anisotropy of the QD shape can lead to the opposite sign of splitting with respect to angular momentum projection ±3/2, ±1/2 for spatially odd (1P3/2) and even (1S3/2) levels of the hole. At the same time, in the case of the potential of an infinitely deep quantum well, an inversion of the order of 1S3/2 and 1P3/2 levels can be observed at values of the ratio of the effective masses of the light and heavy holes β = mlh/mhh ≈ 0.14. The type of the trial wave functions of the hole for the state 1P3/2 in the potential of an isotropic three-dimensional harmonic oscillator depending on β is proposed. The dependence of the binding energy of excitons in the considered potentials on β is presented and the possibility of formation of various biexcitonic states is considered. 相似文献
9.
R. B. Morgunov E. V. Kurganova S. M. Aldoshin N. A. Sanina T. N. Rudneva 《Physics of the Solid State》2007,49(9):1723-1730
The magnetic properties of the binuclear nitrosyl-iron complexes Fe2(SC3H5N2)2(NO)4 are investigated. It is demonstrated that several types of particles, such as dimers with a pair of spins 1/2, dimers with a pair of spins 5/2, and paramagnetic particles with spin 3/2, make a contribution to the magnetic properties of the complexes. A decrease in the temperature below 25 K leads to a change in the shape of the EPR spectra corresponding to these dimers, so that Lorentzian lines (homogeneous broadening) transform into Gaussian lines (inhomogeneous broadening). This is accompanied by a stepwise change in the EPR line width and g factors. The change in the line shape indicates that complexes become asymmetric at low temperatures, possibly, due to the decrease in the spin exchange frequency below the frequency of the microwave field of the spectrometer. 相似文献
10.
A. V. Nagornyi M. V. Avdeev O. V. Yelenich S. O. Solopan A. G. Belous A. V. Shulenina V. A. Turchenko D. V. Soloviov L. A. Bulavin V. L. Aksenov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2018,12(4):737-743
Structural aspects of powders containing magnetic nanoparticles Fe3O4/CoFe2O4 with the anticipated “core-shell” structure are considered by means of comparative analysis with individual particles of Fe3O4, CoFe2O4 in accordance of data obtained from X-ray powder diffraction and small-angle scattering of X-ray (synchrotron) radiation and neutrons. It is shown that magnetic particles in the powders under study have a strong polydispersity and form complex aggregates. Characteristic sizes of the crystallites, as well as a ratio of magnetite to cobalt-ferrite in the composition of the Fe3O4/CoFe2O4 particles were evaluated from the analysis of the diffraction peaks. Аnalyzing the data on small-angle scattering, the dimensional characteristics of particles and aggregates, as well as the volume fraction of the last ones in the powders, have been obtained. Fractal dimensions of aggregates are determined. A significant difference is observed in the scattering on Fe3O4/CoFe2O4 particles and the total scattering consisting of partial contributions to scattering on individual magnetite (Fe3O4) and cobalt-ferrite (CoFe2O4) powders, which does not exclude the formation of the “core-shell” structure. 相似文献
11.
J. Moc 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(3):309-317
We have explored the lowest doublet and quartet potential
energy surfaces (PES) for the reaction of gallium trimer with H2. This
reaction was studied experimentally by Margrave and co-workers in a noble
gas matrix. The detailed reaction paths ending up with the low-energy
Ga3H2 hydride isomers have been predicted based on the high level
ab initio coupled-cluster calculations (CCSD(T)) with large basis set. We
have found that the reaction occuring on the lowest doublet PES is described
by the activation barrier for H2 cleavage of about 15 kcal/mol,
consistent with experiment. In the most stable Ga3H2 hydride
structure, whose formation is exothermic by 15 kcal/mol, both H atoms assume
three-fold bridged positions. The diterminal planar structure of
Ga3H2, proposed experimentally from the observed IR spectra, is
found to be only 1 kcal/mol less stable than the dibridged form. 相似文献
12.
B. H. Yang P. C. Stancil 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(3):351-358
Quantum close-coupling and coupled-states approximation
scattering calculations for rotational energy transfer
of rotationally excited NH3 and ND3 due to collisions with He
are presented. Calculations were performed for collision
energies between 10-5 and 10 000 cm-1
using the NH3-He potential of Hodges and Wheatley [J. Chem. Phys.
114, 8836 (2001)]. State-to-state and total quenching cross sections from
some selected initial states are presented.
Rate coefficients for ortho-NH3 for the quenching 10+→00+
transition were obtained on potentials scaled to reproduce measurements
of second virial coefficients with the results showing strong sensitivity
to the potential, especially at low temperatures. Significant isotope
effects are found in quenching cross sections in the cold to ultracold
regime particularly in the region dominated by quasi-bound resonances,
~0.1 to 10 cm-1. As ammonia has been translationally cooled
via Stark deceleration methods, it is a good candidate for experimental
study of such effects at cold temperatures.
Comparison of rate coefficients with available theoretical results
are also presented. 相似文献
13.
Both a quantum molecular dynamic method and high level ab initio calculations (MP2, CCSD(T)) have
been used to investigate the mechanism of the C3 + H3+ reaction, which is part of the ion
chemistry in interstellar clouds. Furthermore statistic initial orientations in collision simulations
have been set up in order to determinate reaction cross-sections and rate coefficients of all occurring
reaction channels. Our analysis shows that the revealed mechanism is
strongly determined by dynamic effects. 相似文献
14.
A. V. Burenin 《Optics and Spectroscopy》2010,108(4):506-511
The internal dynamics of the isotopically asymmetric ionic complexes ArH2D+ and ArD2H+ is considered to be a distorted dynamics of the isotopically symmetric ArH3+ complex. By using the group chain methods, a rigorous algebraic model is constructed to describe the spectrum of the asymmetric
complexes with an allowance for the torsional motion of the structure of hydrogen nuclei. The model is based on the geometrical
group of symmetry of internal dynamics of the isotopically symmetric ionic complex, which is used here as a noninvariant group. 相似文献
15.
H. Martínez F. B. Yousif 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(3):493-498
This paper considers the electrical and optical characterization of glow
discharge pulsed plasma in N2/H2 gas mixtures at a pressures range
between 0.5 and 4.0 Torr and discharge current between 0.2 and 0.6 A.
Electron temperature and ion density measurements were performed employing a
double Langmuir probe. They were found to increase rapidly as the H2
percentage in the mixture was increased up to 20%. This increase slows
down as the H2 percentage in the gas mixture was increased above 20%
at the same pressure. Emission spectroscopy was employed to observe emission from the pulsed
plasma of a steady-state electric discharge. The discharge mainly emits
within the range 280–500 nm. The emission consists of N2 (C-X) 316, 336,
358 nm narrow peaks and a broad band with a maximum at λmax = 427 nm. Also lines of N2, N2
+ and NH excited states were
observed. All lines and bands have their maximum intensity at the discharge
current of 0.417 A. The intensities of the main bands and spectral lines are
determined as functions of the total pressure and discharge current.
Agreement with other theoretical and experimental groups was established. 相似文献
16.
Xiaohua Jia Huiqing Fan Xiangdong Lou Jiaqiang Xu 《Applied Physics A: Materials Science & Processing》2009,94(4):837-841
The CdSnO3 semiconducting oxide that can be used as a gas-sensitive material for detecting ethanol gas is reported in this paper. CdSnO3 nanoparticles were prepared by a chemical co-precipitation synthesis method, in which the preparation conditions were carefully
controlled. The n-type gas-sensing semiconductors were obtained from the as-synthesized powders calcined at 600°C for 1 h.
The phase and microstructure of the obtained nanoparticles were characterized by X-ray diffraction (XRD), transmission electron
microscopy (TEM), and Brunauer–Emmett–Teller (BET) method with a gas adsorption analyzer. CdSnO3 has a small particle size range of 30–50 nm and a high surface area of 9.12 m2/g, and a uniformity global shape. The gas sensitivity and operating temperature, and selectivity of CdSnO3-based sensors were measured in detail. The gas sensors fabricated by CdSnO3 nanoparticles had good sensitivity and selectivity to vapor of C2H5OH when working temperature at 267°C, the value of gas sensitivity at 100 ppm of C2H5OH gas can reach 11.2 times. Furthermore, gas-sensing mechanism was studied by using chromatographic analysis. 相似文献
17.
We have carried out experimental and theoretical
studies on electron scattering from the C3H6 isomers and
C3F6 molecules and we report on total, differential as well
as theoretical integral elastic cross-sections for these
molecules. Vibrational excitation functions are also presented for
the typical vibrational peaks in C3H6 and cyclo-C3H6
for the angle of 90○, impact energy range of 1–16 eV
and loss energies of 0.12 eV and 0.13 eV, respectively. In the
cross-sections, clear differences in peak positions and magnitudes
between the C3H6 isomers can be viewed as the isomer effect.
The same is observed between C3H6 and C3F6 in a clear
manifestation of the fluorination effect. The resemblance of the
π* shape resonance in the cross-sections, observed at about
2.2 eV for C3H6 and 3.5 eV for C3F6, to those in
C2H4 and C2F4 clearly points to the effect of the
double bond in the molecular structures for these molecules.
Theoretical analysis is performed to provide rationales for the
scattering dynamics. 相似文献
18.
Dr. Minakshi L. K. Jha S. N. Chatterjee B. N. Roy 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,51(3):331-339
H+ and He2+ impact single and double ionization cross
sections of ground state lead atoms have been calculated in the binary
encounter approximation. Calculations of direct double ionization cross
sections have been performed in the modified double binary encounter model.
The accurate expressions of σΔE (cross-section for energy
transfer ΔE) and Hartree-Fock velocity distributions for the target
electrons have been used throughout the calculations. Contributions to
double ionization from Auger effect following ionization of inner shells
have been considered in the present work. Our H+ impact single and
double ionization cross sections are in good agreement with the experimental
observations. In calculations of He2+ impact cross sections, the
present theoretical approach shows limited success in the experimentally
investigated region (50–350 keV amu-1). 相似文献
19.
S. Kang Y.-M. Liu T.-Y. Shi 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(1):37-42
The energy spectra of H2
+-like impurities confined in
finite spherical quantum dots have been calculated as a function
of the distance between nuclear with different sizes on the basis
of effective-mass approximation by linear variational method.
B-splines have been used as basis functions, which can easily
construct the trial wavefunctions with appropriate boundary and
cusp conditions. The quantitative analyses of the partial wave
weights for ground state and some low lying states have been done. 相似文献
20.
β-Ga2O3 nanowires have been synthesized using Ga metal and H2O vapor at 800 °C in the presence of Ni catalyst on the substrate. Remarkable reduction of the diameter and increase of the
length of the Ga2O3 nanowires are achieved by separation of Ga metal and H2O vapor before they reach the substrate. Transmission electron microscopy analyses indicate that the β-Ga2O3 nanowires possess a single-crystalline structure. Photoluminescence measurements show two broad emission bands centered at
290 nm and 390 nm at room temperature.
Received: 27 June 2002 / Accepted: 7 October 2002 / Published online: 17 December 2002
RID="*"
ID="*"Corresponding author. Fax: +886-6/234-4496, E-mail: wujj@mail.ncku.edu.tw 相似文献