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1.
The spectral and polarization characteristics of trans-isomers ofβ-carotene, lycopene, retinal, and 1,6-diphenylhexatriene (DPH) in solutions have been investigated by the methods of polarized fluorescence and semiempirical calculations of AM1 and RM3. The high and constant values of the degree of polarization P ∼0.46, closely coinciding with the limiting value P0=0.5, according to the S2→S0-fluorescence and S2←S0-fluorescence excitation spectra ofβ-carotene and lycopene in n-hexane at room temperature and also high and coinciding according to the S1→S0-fluorescence and S2←S0-fluorescence excitation spectra for retinal in EPA at 77 K and DPH in a polyvinylbutyral film, point to the coincidence of the directions of absorption and emission oscillators. These oscillators are aligned along the major axis of the polyene molecule, and the longwave S2←S0-absorption band is formed only by one electronic1B u +1A g -transition. The oscillators of shortwave Sa←S0-absorption bands are aligned at an angle to the oscillators of the S2←S0-transitions, which is related to the distortions in the structure of molecules (β-carotene, lycopene) or, as in the case of DPH, to the influence of transitions localized on the orbitals of phenyl rings and polarized perpendicularly to the major axis of the molecule. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 1, pp. 69–74, January–February, 2000.  相似文献   

2.
We have investigated the spectral characteristics, quantum yield ϕF, lifetime τF, and polarization of fluorescence of NH-isomers of dibenzobarrelene disubstituted tetraazaisobacteriochlorin at 293 and 77 K. The following information has been obtained from low-temperature measurements: 1) the weak shoulder on the edge of the long-wavelength 0-0 absorption band disappears at 77 K and, therefore, can be assigned to the cis-NH-isomer [the principal component of the tautomeric mixture is the trans-isomer a (b)]; 2) the low value of ϕF at room temperature is due to temperature-viscosity quenching whereas ϕF at 77 K is close to 1 and τF = 5.3 nsec; 3) the energy of the weak electronic transition G → Q2 and the interval have been determined. Quantum-chemical calculations found that replacing the methine bridges by nitrogen stabilizes the non-aromatic trans-isomer a (b) whereas the non-planarity of the macrocycle and the alternation of bond lengths increase for the cis-isomers. The calculated electronic absorption spectra of the a isomer reproduce rather well the experimental data. It is shown that the four-orbital model is applicable for the lower excited states Q1 and Q2 for all NH-isomers. __________ Translated from Zhurnal Prikladnoi Spektroskopii Vol. 74, No. 3, pp. 395–407, May–June, 2007.  相似文献   

3.
The effect of deuteration of the central NH groups on the quasi-linear fluorescence and fluorescence excitation (with selective monitoring) spectra for triazatetrabenzoporphine, a close analog of phthalocyanine, has been investigated at 77K in n-nonane. Vibrational analysis of the spectra was carried out. The normal mode frequencies were determined for the electronic states S0 (from fluorescence spectra) and S1 (for fluorescence excitation spectra). It has been established that N-deuteration lowers the frequency of a vibration involving inplane NH bending down to ∼990 cm−1 and leads to resonant vibrational-electronic (vibronic) interaction of Fermi-type resonance between the zero level of the S2 state and the vibronic level of the S1 state upon excitation of this mode. Thereby the possibility of the “vibronic analog of Fermi resonance” (a term coined by G. Herzberg) occurring in a simple (two-component) variant of phthalocyanine-type molecules has been shown. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 796–803, November–December, 2008.  相似文献   

4.
In selective laser excitation and at T=4.2 K, fine-structure spectra of the fluorescence of the complexes of Mg, Zn, In, and TiO with octaethylporphyrin are obtained. It is shown that the fine-structure fluorescence spectra of these compounds are formed to a large aegree by ribronic interaction between quasi-degenerate S1 and S2 electron states. An increase in the relative intensities of a number of negatively polarized fluorescence lines in displacement of the excitation line from a longwave edge of the band of an S0→S1 transition in the shortwave direction is revealed. Reported at the VIIIth International Conference on Spectroscopy of Porphyrins and Their Analogs, Minsk, September 22–26, 1998. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 518–522, July–August, 1999.  相似文献   

5.
Er3+ clustering phenomenon in Ga–Ge–S chalcogenide system is studied using Raman spectroscopy. The Raman spectra from 10 to 500 cm−1 for glasses (100−y)[15Ga2S3–85GeS2]–yEr2S3 (y=0.08−5.00 mol. %) have been analyzed. To reveal the influence of the chemical composition on the glass structure the intensity of the peak corresponding to Ge–Ge (Ga–Ga) homopolar bonds has been examined. The peak intensity increase with Er2S3 concentration change in the region 0<C(Er2S3)<2 mol. % has been interpreted in terms of the sulphur deficiency in the glass resulting in the formation of S3Ge–GeS3 (S3Ga-GaS3) structural units. The further increase in concentration beyond 2 mol. % reduces the sulphur deficiency, which can be attributed to the formation of the ternary compound Er3GaS6. The structural units Er3GaS6 contain a large mol. fraction of Er3+ or, in other words, Er3+ clusters. The data obtained from the low-frequency Raman spectra (boson band) indicate strong variations of the medium-range order (MRO) in the glasses induced by Er3+. The observed behavior of the MRO size (the correlation length) with increasing of Er2S3 concentration provides for additional evidence of the Er3+ clustering.  相似文献   

6.
The locations of the 000 0_0^0 -bands for S1← S0 and S1 → S0 transitions have been found for C60 solutions in hexane. It is shown that the profile of the S1 ← S0 band is mainly shaped by hu(4), t1u(4)- and hg(1), ag(2)- modes that are active in absorption. Bands involving the hu(4)- and t1u(4)-modes in the emission process have also been identified in the fluorescence spectrum. The appearance of the 000 0_0^0 -band in the forbidden 11T1g ← 11Ag transition is explained by symmetry reduction in the C60+environment system due to the interaction of electrons with local phonons. The temperature coefficients of the red shift for the 256.3- and 328.3-nm bands of allowed 1T1u ← 11Ag transitions for C60 in hexane are equal to –1.45 and –0.46 cm–1·K–1, respectively. The peak and half-width values of the 337.2-nm band for C60 in polystyrene remain unchanged on cooling to 77 K. Absorption in the 700–800-nm region for concentrated hexane solutions of fullerene at 292 K results from the production of (C60)n-clusters.  相似文献   

7.
0 –S1–Sm–Sn multilevel system. An Sm→S1 absorption recovery time of τS1 A=(600±100) fs is determined. The picosecond and femtosecond pulse excitation leads to S0→S1 ground-state absorption bleaching and S1→Sm first excited-state absorption bleaching. The excited-state absorption cross-sections σS1 ex(S1→Sm) and σSm ex(Sm→Sn) are determined. Received: 3 June 1996  相似文献   

8.
We have studied the effect of lead dopant on the optical absorption, photoluminescence, and x-ray luminescence spectra, and the scintillation characteristics of CdI2 at room temperature. The crystals for the study were grown by the Stockbarger-Bridgman method. Activation of CdI2 from the melt by the compound PbI2 leads to the appearance in the absorption spectra in the near-edge region of an activator band at 395–405 nm, which is interpreted as an A band connected with electronic transitions from the 1S0 state to the 3P1 levels in the Pb2+ ion. For x-ray excitation, CdI2:Pb2+ crystals with optimal dopant concentration (∼1.0 mol%) are characterized by a light yield with maximum in the 570–580 nm region that is an order of magnitude higher than for CdI2 crystals in the 490–500 nm band. For α excitation, the radioluminescence kinetics for cadmium iodide is characterized by a very short (∼0.3 nsec) rise time and fast decay of luminescence, with τ1 ≈ 4 nsec and τ2 = 10–76 nsec. Depending on the conditions under which the crystals were obtained, the fast component fraction is 95%–99%. The crystal is characterized by a similar scintillation pulse in the case of excitation by x-ray pulses. The radioluminescence pulse shape for CdI2:Pb in the decay stage is predominantly exponential, with luminescence decay time constants τ1 ≈ 10 nsec and τ2 = 200–250 nsec. This system is characterized by low afterglow, at the level for the Bi4G3O12 scintillator. We have demonstrated the feasibility of using CdI2:Pb as a scintillator for detecting α particles. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 825–830, November–December, 2008.  相似文献   

9.
The quasiline spectra of the fluorescence and absorption of bisanthene in n-hexane are obtained at 77 and 4.2 K, and their vibration analysis is carried out. Substantial violation of the mirror symmetry of the fluorescence and S1 ← S0-absorption bands with respect to both the frequencies and intensities is found. This allowed the conclusion that the S2-level is localized in the region of vibronic sublevels of the S1-state with . Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 4, pp. 488–491, July–August, 2000.  相似文献   

10.
Hydrobenzophenanthrolinone derivatives were synthesized by three-component condensation of 8-aminoquinoline, aromatic aldehydes, and dimedone. The structures of the obtained substances were confirmed by NMR and IR spectroscopy and mass spectrometry. Spectral-luminescent investigations of the synthesized compounds showed that they were characterized by high oscillator strengths for allowed electronic transitions S n S 0 (n = 1–3). Low fluorescence quantum yields in EtOH (Φfl ~ 10–4–10–3) and an increase of the Φfl values in toluene (~10–2) at room temperature and with lowering the temperature to 77 K (Φfl ~ 10–1) for a number of the compounds under study were satisfactorily explained within the framework of Marcus theory.  相似文献   

11.
Four praseodymium complexes of aromatic carboxylates (benzoate, 4-tert-butylbenzoate, 2-benzoylbe-noate, and benzimidazole-5-carboxylate) have been synthesized and characterized, whose photophysical properties have been studied with ultraviolet spectra, phosphorescence spectra, and fluorescence spectra. The fluorescent emission spectra of all praseodymium complexes show two emission peaks under the excitation band of 245 nm at about 395 and 595 nm respectively, while one peak under 415 nm at about 595 nm, which attributed to be 1S01I6 (395 nm) transition and the characteristic emission 1D23H4 (595 nm) transition of Pr3+ ion. The 1S01I6 transition can be ascribed as the transition of charge transfer state, and the 1D23H4 can be further proved that there exists an antenna effect in the fluorescence of praseodymium with aromatic carboxylic acids. In conclusion, the praseodymium complexes systems can realize the double fluorescent conversion in both ultraviolet and visible region and can be further studied the application of this conversion.  相似文献   

12.
Conformations of He-jet-cooled trimethyl[(3-indole)ethoxy]silane (TIES) have been studied using a laser spectroscopy technique in combination with quantum-chemical computations. Six probable conformers of the molecule were computed, of which only two conformations were observed. Based on an analysis of fluorescence excitation spectra, fluorescence spectra, shapes of rotational band contours at the electronic S0–S1 transition of TIES, and theoretical computations, the above conformers were assigned to steric structures. Twisted structures have the lowest energy due to intramolecular hydrogen bonds C - H ?O < CSi C - H \cdots O <_C^{Si} between hydrogen atoms of methyl groups and an oxygen atom and C–H···π between H and the π-electron cloud of the indole ring.  相似文献   

13.
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   

14.
    
The optical constants of crystal quartz in the far infrared (10 – 600 cm−1) are reported at room temperature and at 10 K, for both polarizations parallel and perpendicular to the c-axis, respectively extraordinary and ordinary ray. These constants are obtained from the analysis of the transmissivity channeled spectra below 300 cm−1, and from the analysis of the reflectivity spectra between 300 – 600 cm−1, measured by using a grating infrared spectrometer. The extrapolated zero frequency refractive indices of quartz obtained in the present work are: no(0) = 2.106 and ne(0) = 2.153 at 300 K; no(0) = 2.072 and ne(0) = 2.130 at 10 K.  相似文献   

15.
We have studied the spectral luminescence properties of a zinc complex of dibenzobarreleno-substituted tetraazaisobacteriochlorin (a synthetic tetrapyrrole pigment which is the structural analog of the biologically important chromophore isobacteriochlorin) and a palladium complex of dibenzobarreleno-substituted tetraazachlorin. We have shown that despite the substantial effect of aza-substitution on the electronic structure and the electronic spectra of the tetrapyrrole molecules, the effect of hydrogenation of adjacent pyrrole rings on the spectral luminescence properties is similar in compounds with nitrogen and carbon bridges. As in the free base case, the fluorescence of the studied zinc complex is strongly quenched at 293 K but flares up at 77 K (temperature and viscosity-dependent quenching). To study the substituted Zn-tetraazaisobacteriochlorin, we determined the position of the 0-0 band of the low-intensity transition S0 → S2 and showed that the S2 → S1 energy difference increases with bridge aza substitution. For the Pd complex of dibenzobarreleno-substituted tetraazachlorin, we could not detect phosphorescence in the near IR region (to 1150 nm); we detected weak fluorescence. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 5, pp. 700–707, September–October, 2008.  相似文献   

16.
While studying the effect of thermal treatment at 625–700°C on the formation of borosilicate glass-embedded CdSe or CdSe1−x S x nanocrystals, pronounced bands at 323 and 646 cm−1 were observed in the Raman spectra. They are assigned to Se2 clusters on the base of their frequency positions, widths, intensities, and resonance behavior. The precipitation of Se2 molecular clusters in borosilicate glass is shown to occur when the heat treatment temperature and/or duration are beyond the range, most suitable for the formation of CdSe or CdSe-rich CdSe1−x S x nanocrystals.  相似文献   

17.
A measurement of the 2S Lamb shift in muonic hydrogen (μp) is being prepared at the Paul Scherrer Institute (PSI). The goal of the experiment is to measure the energy difference ΔE(25 P 3/2−23 S 1/2) by laser spectroscopy (λ≈6μm) to a precision of 30 ppm and to deduce the root mean square (rms) proton charge radius with 10−3 relative accuracy, 20 times more precise than presently known. An important prerequisite to this experiment is the availability of long-lived μp2S -atoms. A 2S-lifetime of ∼1 μs – sufficiently long to perform the laser experiment – at H2 gas pressures of 1–2 hPa was deduced from recent measurements of the collisional 2S-quenching rate. A new low-energy negative muon beam yields an order of magnitude more muon stops in a small low-density gas volume than a conventional cloud muon beam. A stack of ultra-thin carbon foils is the key element of a fast detector for keV-muons. The development of a 2 keV X-ray detector and a 3-stage laser system providing 0.5 mJ laser pulses at 6 μm is on the way. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

18.
A simple and sensitive chemiluminescence (CL) method coupled with flow-injection technique is proposed to determine naproxen (NAP). The method is based upon the enhancement of the weak CL signal arising from the reaction of Ce(IV) and Na2S2O4 with Eu3+ to form the Eu3+-Ce(IV)-Na2S2O4 system. The CL intensity was significantly increased by the introduction of NAP into this system in the presence of silver nanoparticles (Ag NPs). Examination of the recorded UV–vis spectra and fluorescence spectra indicated that the energy of the intermediate SO2*, which originated from the redox reaction of Ce(IV) and Na2S2O4, was transferred to Eu3+ via NAP and that the process was accelerated by Ag NPs due to their catalytic activity. Under the optimum conditions, the CL intensity was increased with increasing NAP concentration and the correlation was linear (r = 0.9992) over the NAP concentration range of 1–420 ng mL−1. The limit of detection (LOD) was 0.11 ng mL−1 with a relative standard deviation (RSD) of 1.15% for 5 replicate determinations of 200 ng mL−1 NAP. The method was successfully applied to determine NAP in pharmaceutical and biological samples.  相似文献   

19.
Bi2S3 nanotubes and de-doped poly(3,4-ethylenedioxythiophene) (PEDOT) composite nanopowders were synchronously synthesized by a one-pot self-assembly method. The powders were characterized by X-ray powder diffraction, infrared spectroscopy, and transmission electron microscopy, respectively. Thermoelectric properties of the Bi2S3–PEDOT composite nanopowders with different Bi2S3 contents after being cold pressed into pellets were measured at room temperature. The sample with 36.1 wt% Bi2S3 has a highest power factor of 2.3 μWm−1K−2, which is higher than that of both pure PEDOT (0.445 μWm−1K−2) and Bi2S3 (1.94 μWm−1K−2).  相似文献   

20.
2 +? O2→H2O on polycrystalline Pt foils has been studied by detection of desorbing OH radicals using the Resonance Enhanced Multiphoton Ionization, REMPI, technique. The measurements were performed at catalyst temperatures of 1000–1400 K and a total pressure below 10-4 mbar. The studies of OH desorption by REMPI were achieved using a two-photon excitation D2Σ-–X2Π (1–0), followed by one-photon ionization. The ions were detected in a time-of-flight mass spectrometer, TOF-MS, in order to avoid interference from non-resonantly ionized molecules. By applying TOF-MS, a simultaneous non-resonant ionization and detection of H2, O2 and H2O was achieved. Recorded REMPI spectra were compared with spectra simulated using known molecular constants. The kinetics of the reaction derived from the measurements were compared with what was obtained in earlier LIF detection of OH, performed at higher total reactant pressure using the A–X transition. REMPI TOF-MS is shown to be a complement to LIF for reaction studies below 5×10-4 mbar total pressure, where LIF is too insensitive for quantification. The reaction kinetics was found to be in agreement with a theoretic model and previous LIF studies. Received: 8 March 1996/Revised version: 4 October 1996  相似文献   

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