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1.
G. A. Zalesskaya D. L. Yakovlev E. G. Sambor D. V. Prikhodchenko 《Journal of Applied Spectroscopy》2001,68(1):150-158
By the delayed fluorescence activated by direct multiphoton excitation of triplet molecules by CO2–laser radiation we have studied the prevailing deactivation pathways of triplet molecules with a high store of vibrational energy E
vib. The dependences of the kinetic characteristics of delayed fluorescence on the presence of vapors and foreign gases have been used to estimate the rates and efficiencies of intermolecular vibrational relaxation in the vibrational quasi–continuum of the triplet state T
1. By the changes in the intensities and decay rates over a wide range of vibrational energies we have established the E
vib dependences of reversible intercombination conversion between the states T
1 and S
1 and interconversion from T
1 to the ground electronic state S
0 for both the case of isolated excited molecules and at a steady vibrational temperature. It is shown that at high vibrational temperatures the radiationless transition from the T
1 state to S
0 has an activation character and is accomplished through the energy barrier. The conditions for going to an exponential dependence have been determined. It has been found that the obtained dependences are in good agreement with the known experimental results. The influence of molecular and environmental characteristics on the decay rate of triplet molecules is compared. 相似文献
2.
G. A. Zalesskaya 《Journal of Applied Spectroscopy》1998,65(5):701-721
Results of investigations of the process of multiphoton excitation of polyatomic molecules by CO2-laser radiation are presented. The mechanism of formation of the profiles of IR absorption bands of polyatomic molecules
is discussed. New experimental methods of investigation of relaxation processes at high levels of vibrational excitation of
molecules in the ground and triplet states are considered. For vapors of polyatomic molecules and their mixtures with foreign
gases, the quantitative characteristics of the collisional exchange and the vibrational-energy transfer as well as the rates
of intercombinational conversion ⇛ and triplet-triplet transfer are presented and their dependences on the vibrational-excitation
level are discussed.
Institute of Molecular and Atomic Physics of the National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072,
Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 5, pp. 675–693, September–October, 1998. 相似文献
3.
It is usually very difficult to directly obtain molecular dissociation energy D
e and all accurate high-lying vibrational energies for most diatomic electronic states using modern experimental techniques
or quantum theories, and it, is also very difficult to give accurate analytical expression for diatomic molecular dissociation
energy. This study proposes a new analytical formula for obtaining accurate molecular dissociation energy based on the LeRoy
and Bernstein’s energy expression in dissociation limit. A set of full vibrational energy spectra for some electronic states
of N2 molecule are studied using the algebraic method (AM) suggested recently, and the corresponding accurate molecular dissociation
energies are evaluated using the proposed new formula and high-lying AM vibrational energies. The results show that the AM
spectra and the new theoretical dissociation energies agree excellently with experimental data, and thereby providing a new
physical approach to generating accurate dissociation energies for electronic states of diatomic molecules. 相似文献
4.
5.
The vibrational kinetics of CW CO2 lasers has been analyzed within the framework of a temperature model. The necessity of taking into account the coupling of the vibrational modes of the CO2 molecule in determining the occupation numbers and the store of vibrational energy in individual modes is shown. Expressions that connect vibrational temperatures with the rates of excitation and relaxation of the lower vibrational levels of modes have been obtained. The ratios between the vibrational temperatures on selective excitation of the 00° 1 level and on excitation of CO2 molecules in an electric discharge as well as the character of the dependences of vibrational temperatures on the pumping-energy value are discussed.__________Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 1, pp. 72–79, January–February, 2005. 相似文献
6.
I. N. Ogorodnikov I. N. Sedunova L. I. Isaenko S. A. Zhurkov 《Physics of the Solid State》2012,54(3):485-492
This paper reports on a study of the luminescence emitted by Li6Gd(BO3)3: Ce3+ crystals under selective photoexcitation to lower excited states of the host ion Gd3+ and impurity ion Ce3+ within the 100–500-K temperature interval, where the mechanisms of migration and relaxation of electronic excitation energy
have been shown to undergo noticeable changes. The monotonic 10–15-fold increase in intensity of the luminescence band at
3.97 eV has been explained within a model describing two competing processes, namely, migration of electronic excitation energy
over chains of Gd3+ ions and vibrational energy relaxation between the 6
I
j
and 6
P
j
levels. It has been shown that radiative transitions in Ce3+ ions from the lower excited state 5d
1 to 2
F
5/2 and 2
F
7/2 levels of the ground state produce two photoluminescence bands, at 2.08 and 2.38 eV (Ce1 center) and 2.88 and 3.13 eV (Ce2
center). Possible models of the Ce1 and Ce2 luminescence centers have been discussed. 相似文献
7.
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10.
The specific features of the triplet-triplet (T-T) transfer of electronic excitation energy in a gas phase upon nonequilibrium
vibrational excitation of the triplet molecules of a donor were studied for an anthraquinone-diacetyl donor-acceptor pair
using the time-resolved slow fluoresence of anthraquinone and sensitized phosphorescence of diacetyl. It is shown that in
the gas phase, which allows regular control of the number of collisions, competition between the processes of T-T transfer
and intermolecular vibrational relaxation is observed for nanosecond time resolution. The T-T transfer rate for the molecular
system investigated exceeded the rate of intermolecular vibrational relaxation kV in the triplet state T1 of the donor. The effectiveness of the T-T transfer of energy by vibrationally excited molecules turned out to be higher
than the effectiveness of transfer by thermalized ones, but even the highest of them was much less than unity. An increase
in the equilibrium temperature of vapors led to a decrease in the effectiveness of transfer for both vibrationally excited
and thermalized triplet molecules, thus indicating the importance of the collisional complex in the intermolecular process
studied.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 4, pp. 474–479, July–August, 2000. 相似文献
11.
Yoshitake Suganuma Yasuyuki Kowaka Noritaka Ashizawa Naofumi Nakayama Hitoshi Goto Takayoshi Ishimoto 《Molecular physics》2013,111(14):1831-1840
We observed fluorescence excitation spectra and dispersed fluorescence spectra for single vibronic level excitation of jet-cooled perylene-h 12 and perylene-d 12, and carefully examined the vibrational structures of the S0 1 A g and S1 1 B 2u states. We performed vibronic assignments on the basis of the results of ab initio calculation, and found that the vibrational energies in the S1 state are very similar to those in the S0 state, indicating that the potential energy curves are not changed much upon electronic excitation. We conclude that the small structural change is the main cause of its slow radiationless transition and high fluorescence quantum yield at the zero-vibrational level in the S1 state. It has been already reported that the lifetime of perylene is remarkably short at specific vibrational levels in the S1 state. Here, we show that the mode-selective nonradiative process is internal conversion (IC) to the S0 state, and the ν16(a g ) in-plane ring deforming vibration is the promoting (doorway) mode in the S1 state which enhances vibronic coupling with the high-vibrational level (b 2u ) of the S0 state. 相似文献
12.
Jana Páleníková Michal Kraus Pavel Neogrády Miroslav Urban 《Molecular physics》2013,111(20):2333-2344
Geometries, excitation energies, dipole moments and dipole polarisability tensor components of the ground and four lowest excited states 3 B 1, 1 B 1, 3 A 2, 1 A 2 of the H2O and H2S molecules were calculated at the CASSCF, CASPT2, CCSD and CCSD(T) level of approximation. Vertical excitation and equilibrium transition energies of these states, having the Rydberg character, are reported too. Properties of both molecules in the ground and in low lying excited states are compared and discussed from the point of view of their molecular electronic structure. Upon excitation we observe dramatic changes of dipole moments and polarisabilities with respect to the ground state. We stress the change of the polarity of H2O in all excited states accompanied by the enhancement of the dipole polarisability by an order of magnitude. Large, even if less pronounced, are changes of electric properties of H2S in its excited states. Dipole moments and dipole polarisabilities of 3 B 1, 1 B 1 states of H2S and H2O behave quite analogously in comparison to their respective ground state. The general pattern of properties for both molecules in their 3 A 2 and 1 A 2 excited states is more different due to a pronounced participation of the sulphur d-orbitals in these states of the H2S molecule. 相似文献
13.
Stavros C. Farantos 《Molecular physics》2013,111(4):835-845
A quasiclassical trajectory study has been carried out for collisions of 4He with electronically excited H2(B 1Σ+ u ) and its isotopomer HD. By using analytical fits for the ab initio potential energy surfaces of the ground and the excited state we have obtained vibrational and electronic quenching cross sections for several initial conditions. We draw the following conclusions. Vibrational excitation strongly promotes electronic quenching whereas translational energy is less effective. Rotational excitation decreases the rate of quenching. In a remarkable contrast to the ground electronic state, vibrational energy transfer on the excited potential energy surface is an efficient and fast process. Collisions at high energies results in T → R energy transfer. The above conclusions are valid for both H2 and HD. 相似文献
14.
Accurate studies on the full vibrational energy spectra and molecular dissociation energies for some electronic states of halogen molecule
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This paper obtains accurate vibrational spectroscopic constants and full vibrational energy spectrum by the algebraic method (AM) for some electronic states of halogen diatomic molecules.Motivated by the recent success of obtaining the dissociation energies of Li 2 molecule by using a new analytical formula,it further extends the formula to study the dissociation energies of halogen diatomic molecules.The results show that the AM spectrum and the theoretical dissociation energies agree well with RKR data and experimental data respectively. 相似文献
15.
Previous theoretical work on energy cluster formation at high rotational excitation in the vibrational ground state of PH3 [S.N. Yurchenko, W. Thiel, S. Patchkovskii, P. Jensen, Phys. Chem. Chem. Phys. 7 (2005) 573] is extended to BiH3 and SbH3. By means of variational calculations of the rotation–vibration energies based on ab initio potential energy surfaces, we analyze the rotational energy clustering of BiH3 and SbH3 at J 70 for a number of vibrational states. We show that BiH3 and SbH3, with their pronounced local mode behaviour, exhibit cluster formation already at moderate rotational excitation. In addition, owing to its quasi-spherical-top character, BiH3 undergoes an imperfect bifurcation at high J. This gives rise to an energy cluster type not present in PH3 and SbH3. We present a semi-classical approach to the construction of the rotational energy surfaces for vibrationally excited states. 相似文献
16.
Intermolecular vibrational relaxation is studied in mixtures of polyatomic molecules (benzophenone and fluorene) with bath gases after multiphoton excitation of the triplet molecules by CO2 laser radiation. The dependences of the decay rate and the intensity of laser-induced delayed fluorescence on the laser energy density E CO2 and pressure P fg of bath gases are analyzed. They are found to be different for the fast and slow components of delayed fluorescence, which decays nonexponentially. It is shown that a change in the decay rate of the fast fluorescence component with increasing pressure P fg is governed by the properties of vibration-translation relaxation. The efficiency β of this process is estimated in a broad range of vibrational energies. It is found that β weakly changes with increasing E vib upon excitation of molecules to high vibrational levels. The features of intermolecular vibrational relaxation at high densities of anharmonically coupled vibrational states are discussed. 相似文献
17.
The characteristics of the rapid and retarded fluorescence of the vapor of carbazole excited by the radiation of a nitrogen laser are studied. The dependences of the intensity and rate of decay of the retarded fluorescence on the exciting-radiation intensity, the temperature, and the pressure of the vapor and foreign gases are used to determine the predominant mechanisms of relaxation of triplet molecules. It is shown that the decay of the retarded luminescence is governed by the competition between the processes of triplet-triplet annihilation that lead to the emission of annihilation retarded fluorescence and intercombination conversion of the triplet molecules to the ground electronic state. The characteristic times of these processes and the lifetimes of the triplet state in the vapor
T
are evaluated; the temperature dependence of
T
is analyzed in a wide interval of temperatures (77–573 K). It is inferred that in all aggregative states, the reduction in
T
with increase in the temperature has a common nature and reflects an increase in the rate of intercombination transition T
1 — S
0 with increase in the content of vibrational energy. 相似文献
18.
By the quenching of the delayed fluorescence (DF) of anthraquinone vapors by aliphatic amines (diethylamine, dibutylamine, cyclohexylamine) and pyridine the photoinduced processes proceeding with the participation of vibrationally excited triplet molecules of anthraquinone have been investigated. The DF quenchingrate constants K
q varying from 1·106 sec–1·torr–1 in mixtures with diethylamine to 7·103 sec–1·torr–1 in mixtures with pyridine have been estimated. A correlation between the values of K
q and the ionization potentials of foreign gases confirming the important role of interactions with charge transfer in the quenching of triplet molecules in the gas phase has been established. The influence of other relaxation processes on the DF quenching is considered. It is shown that the intermolecular vibrational relaxation in the T
1 triplet state leading to the establishment of relaxation equilibrium at a vibrational temperature T
vib considerably increasing the medium temperature is the fastest process among the biomolecular processes (rate constants K
col
V > 106 sec–1·torr–1 > K
q). The values of T
vib and the vibrational energies E
vib of the triplet molecules after the energy exchange in the collisional complex have been estimated. It has been concluded that the photochemical reaction yield is determined by the intermolecular processes proceeding in the T
1 state at a vibrational equilibrium characterized by high values of T
vib. The influence of E
vib of triplet molecules on the DF quenching rates at a photoinduced electron transfer is considered. 相似文献
19.
V. N. Bagratashvili Yu. G. Vainer V. S. Doljikov S. F. Koliakov A. A. Makarov L. P. Malyavkin E. A. Ryabov E. G. Silkis V. D. Titov 《Applied Physics A: Materials Science & Processing》1980,22(1):101-105
The method of spectroscopy of spontaneous Raman scattering (RS) with time resolution has been applied for the first time to
diagnose the process of multiphoton ir molecular excitation (MPE). Some aspects of RS diagnostics of MPE processes are being
analyzed. It has been shown experimentally on SF6 and CF3I molecules that it is possible to study such important characteristics of excitation process as the fraction of molecules
involved in the process of excitation, vibrational energy distribution of molecules, stochastization of inner molecular energy. 相似文献
20.
对大多数双原子分子电子态的高阶振动能谱,现代实验方法和量子力学理论计算都难以得到较精确的振动能级.文中应用基于二阶微扰理论的代数方法(AM)以及计算双原子分子离解能的新表达式研究了碱金属双原子分子Li2的33Σ+g,13Δg和23Πg,Na2的B1Πu以及K2的41Σ+g电子态的完全振动能谱{EυAM}和离解能,理论计算结果不仅与已有的实验值相符,而且还给出了实验尚未得到的高阶振动能级.这些结果为碱金属双原子分子精确振动能谱和离解能的科学研究提供了重要数据.
关键词:
碱金属分子
高阶振动能级
离解能
代数方法 相似文献