共查询到20条相似文献,搜索用时 31 毫秒
1.
V. V. Volchkov S. I. Druzhinin J. A. Kossanyi B. M. Uzhinov 《Journal of fluorescence》2000,10(2):161-161
The absorption and fluorescence spectra of five cations protonated at the quinolyl nitrogen atom (IH+–VH+) and one ethylated (IEt+) cation were investigated. For these compounds (except VH+) both an anomalously large fluorescence Stokes shift (up to 238 nm) and a large short-wavelength fluorescence shift (up to 145 nm) at decreasing temperatures (down to 77 K) were observed. This is not the case for unprotonated molecules. The ground-state conjugation between quinolyl and another molecular fragment was found for II, IH+, IIH+, and IEt+. The relaxation process of excited cations is medium viscosity and temperature dependent. The experimental results are explained in terms of excited-state structural relaxation. 相似文献
2.
3.
4.
Electronic structures of Li+ ion-ethylene carbonate (EC) complexes were studied by density functional theory. The structural, electronic and dynamical properties of Li+-EC complexes were studied for both an isolated EC molecule and clusters including Li+ ion. Our structural analysis showed only one type of Li+ coordination with EC through Li+?OC which was supported by the vibration spectral analysis for interaction between Li+ ion and a solvent (EC) molecule. It was analyzed that the solvation energy and Mulliken charge of Li+ ion solvated by EC molecule decrease with increase in number of EC molecule. However, electron affinity shows the opposite change. This analysis with solvation energy, electron affinity and Mulliken charge supported the stabilization of 4-coordinated solvation shell among [Li+(EC)n]n=1-5 complexes. 相似文献
5.
The photoassociation spectrum of an equilibrium vapor of mercury atoms in the range of 34960–37250 cm?1 is recorded with the help of a tunable laser in observations of laser-induced fluorescence. The Franck-Condon fstructure, i.e., periodic variations in absorption intensity against a continuous background, is observed. The structure makes it possible to determine spectroscopic parameters of the upper attractive potential and the lower repulsive potential including that with a van der Waals well. The absorption spectrum of collisional pairs of mercury atoms is calculated using the Numerov-Cooley procedure for integrating the Schrödinger equation. Potential curves of the upper and lower states Hg2(D1u) and Hg2(X0 g + ) are determined by comparing the calculated spectra with the experimental one. 相似文献
6.
F. Stienkemeier J. Higgins W. E. Ernst G. Scoles 《Zeitschrift für Physik B Condensed Matter》1995,98(3):413-416
Large helium clusters, ranging in size from a few hundred to several thousand atoms, are produced in a nozzle expansion. Combining this source with a pick-up scattering cell in which the clusters can be seeded with chromophores allows us to probe the influence of the helium environment on the atoms and molecules attached to the clusters. Using an alkali as chromophore we recorded laser induced fluorescence spectra of Na atoms and molecules attached to helium clusters. Apart from the spectrum of the Na monomer, we have found spectroscopic bands which can unambiguous be assigned to two bound Na atoms. The first of this bands is due to 11
+
(A) 11
g
+
(X) excitations of the covalently bound singlet Na2 molecule while the second is due to 13
g
+
13
+
excitations for the van der Waals bound triplet Na2 dimer. Both bands have been vibrationally resolved. Furthermore we found very large fluorescence intensities in the region 605–635 nm which are likely due to the excitation of a species containing three Na atoms attached to a helium cluster. 相似文献
7.
Changes in the fluorescence intensity of polyanions bearing 4-acryloylbenzo-18-crown-6 units on the addition of cations were studied in a mixed solvent of methanol and water at 30°C. The sensitivity of the change in fluorescence intensities of the polymers toward cations was strongly enhanced compared to that of the corresponding model compound. When alkali metal cations were added, the fluorescence intensity of the polymers decreased in the orders Li+>Na+>Cs+>Rb+>K+ in a methanol-water (19) mixture and Li+>Na+>Rb+>K+Cs+ in a methanol-water (91) mixture. Alkaline earth metal cations and alkylamine hydrochlorides decreased the fluorescence intensity of the polymers in a methanol-water (19) mixture. The cation-dependent decrease in the fluorescence intensity of the polymers was affected by the water fraction in a mixed solvent of methanol and water. 相似文献
8.
D. Schwarzhans D. Zimmermann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(2):193-198
The absorption spectrum of NaAr has been investigated with high resolution using a supersonic beam of molecules and a tunable
dye laser. About 3 300 absorption lines due to the transition A
2
Π ←
X and B
2
Σ ←
X have been observed. In addition, we observed the spectral distribution of the fluorescence for a particular absorption line.
From all experimental data the X
2
Σ
+
interaction potential has been deduced in a fully quantum-mechanical method of approach. The potential is given in terms
of an analytical Hartree-Fock-Dispersion function. For the equilibrium parameters of the X state we get R
e
= 5.01(1) ? and D
e
= 41.6(2)
cm
-1
.
Received 28 August 2002 / Received in final form 15 October 2002 Published online 17 December 2002
RID="a"
ID="a"Now at Knick Elektronische Messger?te, Beuckestr. 22, 14163 Berlin, Germany.
RID="b"
ID="b"e-mail: dz@kalium.physik.tu-berlin.de 相似文献
9.
By calculating the optical spectrum band positions and EPR parameters (g factors, g‖, g⊥ and zero-field splitting D) by diagonalizing the complete energy matrix of 3d8 ions in trigonal symmetry, the defect structure of Ni2+ centre in α-LiIO3 crystal is studied. It is found that to reach the good fits of optical and EPR data between calculation and experiment, the Ni2+ ion should shift by Δz ≈ 0.298 Å along C3-axis and the O2? ions between the Ni2+ ion and Li+ vacancy (V Li) should be displaced away from the V Li by Δx ≈ 0.097 Å because of the electrostatic interaction. The results are discussed. 相似文献
10.
R. Bayer J. Kowalski R. Neumann S. Noehte H. Suhr K. Winkler G. zu Putlitz 《Zeitschrift für Physik A Hadrons and Nuclei》1979,292(4):329-336
The metastable 23 S 1 state and the short lived 23 P states of the helium-like6, 7Li+ ion spectra have been investigated by dye laser saturation spectroscopy in a low-energy Li+ ion-beam and fluorescence light detection. The hyperfine structure splittings of all the levels, the 23 P fine structure intervals and the isotope shift of the 23 S 1-23 P transitions have been measured. These measurements were made by application of a specially constructed tunable dye laser system capable of single-mode laser scans over more than 60 GHz. 相似文献
11.
Mössbauer spectra of alkali tris(malonato) ferrates(III) i.e. M3[Fe(C3H2O4)3].4H2O(M=Li, Na, K, NH4) at 298±2K display a single broad absorption band due to spin lattice relaxation effect. The isomer shift values indicate these complexes to be high spin with octahedral symmetry. The isomer shift shows a decreasing trend with the increase in electronegativity/polarizing power of the substituent cation (Li+, Na+, K+, NH4
+). A linear correlation between isomer shift values and the (Fe-O) stretching freguencies has also been observed. 相似文献
12.
N-(1-Anthryl)-2,4,6-trimethyl-pyridinium (I), N-(2-anthryl)-2,4,6-trimethyl-pyridinium (II) and 10-(1-anthryl)-1,2,3,4,5,6,7,8-octahydro-acridinium cations (III) with anomalously high fluorescence Stokes shift have been investigated. Fluorescence kinetics analysis at various temperatures showed that in the range 293–77 K, the radiative deactivation rate constants (kf) increase by 5.5 to 30 times. The low-temperature time-resolved emission spectra of I–III were found to be consistent with the model: A A* B* where A* is the local excited twisted form and B* is the relaxed more planar, bent conformer of the molecule. The rate constants of the excited relaxed state formation (k1) and back reaction (k–1) of compounds studied were estimated. 相似文献
13.
V. V. Sapunov 《Journal of Applied Spectroscopy》2001,68(5):727-735
For solutions of the complexes of phthalocyanine (PhC) with magnesium (Mg-PhC) and of tetrachloromethyl-PhC with zinc (Zn-PhCCh) in mixtures of glycerin with dimethyl formamide (DMF) and for Zn-PhCCh in toluene and DMF it has been found that the electron absorption spectra substantially depend on the substance concentration. It is shown that these changes are attributable to the association of the molecules of pigments. The number of molecules in the associates and the equilibrium constants for this association are determined. The formation of the trimers of Mg-PhC in binary solutions and the dimers of Zn-PhCCh in toluene, DNF, and binary solutions has been established. It has been found that on association the Q absorption bands of the pigments shift to shorter wavelengths as compared to the bands of the monomers. For the Mg-PhC trimers, the shift is = 1410 cm–1, while for the Zn-PhCCh dimers it is 990 cm–1 in toluene, 930 cm–1 in DMF, and 925 cm–1 in the mixture of DMF with glycerin. It is concluded that the structure of the trimers and dimers is of the type of a stack in which molecules are arranged in parallel one above the other at a distance of 3.5 to 4.0 Å between the planes of the molecules. In association, the fluorescence intensity of the pigments decreases substantially (the decrease corresponds to the decrease in the concentration of the monomer molecules of phthalocyanines), with the fluorescence spectra remaining unchanged. Consequently, the associates of the pigments do not display pronounced fluorescence. 相似文献
14.
The angular distribution of Li 7 + -ions (7–60 keV) scattered by rare gas atoms (He, Ne, A, Kr, X) shows 3–5 characteristic maxima of intensity, which are not observed when electrons of equal energy are scattered by the same atoms. The existence of the maxima can be explained by polarization of the scattering rare gas atoms by the Li 7 + -ions. 相似文献
15.
A new compound, 1-[p-(dimethylamino)benzoyl]-4′-phenyl-semicarbazide (1) was synthesized and showed highly selective response to Cu2+ over other metal ions such as Pb2+, Mg2+, Fe2+, Co2+, Zn2+, Cd2+, Hg2+, Ni2+, Ca2+, Ag+, Na+, K+, and Li+. The control compound, 1-[p-(dimethylamino)benzoyl]-4-phenyl-thiosemicarbazide (2), showed different fluorescence spectral response to Cu2+. A 1:1 complex between Cu2+ and 1 was formed while 1:1 and 1:2 complexes between Cu2+ and 2 were formed. The binding model between the receptor (1 or 2) and Cu2+ was supported by IR spectra, mass spectra, and computation model. 1 possessed higher selectivity towards Cu2+ compared with 2 owing to the difference of complexation ability between urea and thiourea groups. 相似文献
16.
Alexei M. Frolov David M. Wardlaw 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(9):190
We discuss an approach to accurate numerical computations of slowly convergent propertiesin two-electron atoms/ions which include the negatively charged Ps? (e?e+e?)and H? ions, Heatom and positively charged, helium-like ions from Li+ to Ni26+. All these ions areconsidered in their ground 11S-state(s). The slowly convergent properties selected inthis study include the electron-nulceus (r2keN) and electron-electron (r2kee) expectation values for k = 2, 3, 4 and 5. 相似文献
17.
Spectral confirmation of the formation of stable equilibrium complexes (association constant K
as = 2106 M–1) of the Krebs cycle enzyme — malate dehydrogenase (MDH) — and one of the promising photodynamic sensitizers — chlorin e
6 — have been obtained. It is shown that the incorporation of dye molecules into the protein globule of dimeric MDH (each subunit of which contains 4 tryptophan amino acid residues, each binding one molecule of chlorin e
6) is accompanied by quenching of the tryptophan fluorescence of the enzyme. However, despite the overlapping of the fluorescence spectra of tryptophanyls of MDH and the absorption spectrum of chlorin e
6, the fluorescence quenching observed is not caused by singlet-singlet inductive-resonant transfer of energy from the donor to the acceptor. The conclusion has been drawn that the reason for the absence of energy transfer from tryptophanyls to the dye is the more effective intertryptophan migration of energy to one of the most longwave amino acid residues, the quenching of the luminescence of which occurs due to the reversible photoinduced transfer of an electron to chlorin e
6 (formation of a complex with charge transfer). The formation of a complex with charge transfer between chlorin e
6 (when it is excited) and one of the amino acid residues of the enzyme that contact with the dye at its binding site on the protein molecule is also the most noncontradictory explanation of the observed (when bound with MDH) decrease in the quantum yield of fluorescence of chlorin e
6 upon increase in the duration of its quenching. The question of the ability of MDH to act as one of the most sensitive targets responsible for the disturbance of mitochondrial functions and initiation of the apoptosis of tumor cells in the process of photodynamic therapy is discussed.Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 71, No. 6, pp. 749–758, November–December, 2004.This revised version was published online in April 2005 with a corrected cover date. 相似文献
18.
Gowri Ramachandran George Simon Yibing Cheng Trevor A. Smith Liming Dai 《Journal of fluorescence》2003,13(5):427-436
The effects of metal salts (NaCl, CaCl2·2H2O, EuCl3·6H2O and Eu(OAc)3) on the steady state and time resolved fluorescence behaviour of poly(para phenylene vinylene) oligomers containing benzo-15-crown-5 ether units (CE-OPV) have been investigated. The presence of EuCl3 causes a significant (8–9 fold) increase in the fluorescence emission intensity of the OPV segments, as compared to pure CE-OPV, in 99:1 methanol/chloroform solution and a small (9 nm) red shift in the emission maximum. The presence of Na+ or Ca2+ results in less marked increases in fluorescence intensity compared to Eu3+. In the presence of Eu3+ and Na+, the fluorescence intensity increases approximately linearly with metal ion concentration up to a metal ion/CE-OPV molar ratio of 10. The emission enhancement is not related to a simple 1:1 (CE-OPV:metal ion) complex formation process. In contrast, in acetonitrile, CE-OPV shows complex fluorescence quenching behaviour as a function of EuCl3 concentration. This solvent dependence suggests that the emission changes with metal concentration are related to the formation of charge-transferred complexes. The marked changes in fluorescence quantum yield of the PPV backbone due to complexation with metal ions makes CE-OPV a sensitive fluorescent probe for metal ions, or may be exploited for improving the quantum yield of PPV-based devices. 相似文献
19.
The results of ab initio Hartree-Fock calculations of endo-and exohedral C60 fullerene complexes with the Li+ ion and Li2 dimer are presented. The coordination of the Li+ ion and the Li2 dimer in the endohedral complexes and the coordination of Li+ ion in the exohedral complex of C60 fullerene are determined by the geometry optimization using the 3–21G basis set. In the endohedral Li+C60 complex, the Li+ ion is displaced from the center of the C60 cage to the centers of carbon hexa-and pentagons by 0.12 nm. In the Li2 dimer encapsulated inside the C60 cage, the distance between the lithium atoms is 0.02 nm longer than that in the free molecule. The calculated total and partial one-electron densities of states of C60 fullerene are in good agreement with the experimental photoelectron and X-ray emission spectra. Analysis of one-electron density of states of the endohedral Li+@C60 complex indicates an ionic bonding between the Li atoms and the C60 fullerene. In the Li+C60 and Li+@C60 complexes, there is a strong electrostatic interaction between the Li+ ion and the fullerene. 相似文献
20.
We report observation of intense spontaneous amplified radiation of Li2 diffuse violet band in the 4100–4900 Å region. The radiation is strongly enhanced when the lithium vapor in a heat pipe is optically pumped with a pulsed dye laser with the output wavelength tuned to near the Li 2s–4s two-photon resonance transition. The diffuse violet band can probably be assigned to a recently reported triplet bound-free (23
g
a
3
u
+
) transition. It is found that the productions of the molecular diffuse band are contributed from Li atoms as well as Li2 molecules. The excitation functions and their dependence on laser power density are presented and the mechanisms for producing the diffuse bands are discussed.Department of Physics, National Central University, Chung-Li, Taiwan, Republic of Chinabl]References 相似文献