Identification of the SO2 cold vibronic bands in the 32 200–33 300 cm−1 region

Summary The fluorescence excitation spectrum of SO₂ in the 32 200–33 300 cm⁻¹ energy region was recorded, at very low rotational temperature, in a pulsed supersonic jet. The band centres and relative intensities of about 60 well-resolved vibronic bands were determined in this region, which extends the previously available data by 800 cm⁻¹. Single vibronic level fluorescence spectra of two neighbouring vibronic bands in theD-band region along with a few filtered excitation spectra are also presented as an example of the resolution for the listed bands. The authors of this paper have agreed to not receive the proofs for correction.     

Fine fluorescence and absorption spectra of hypericin in a polymer matrix at a temperature of 4.2 K

Monochromatic photoexcitation and selective registration in bands of purely electronic S₁↔S₀ transitions resulted in fine fluorescence and absorption (fluorescence excitation) spectra of hypericin in polyvinylbutyral at a temperature of 4.2 K. Vibration analysis of the spectra is done and conclusions are made about the form of many normal vibrations. It is found that the formation of intramolecular hydrogen bonds in the hypericin structure has a substantial effect on the relative position of the electronic vibrational levels of the pigment molecule. Institute of Molecular and Atomic Physics of the National Academy of Sciences of Belarus, 70, F. Skorina ave., Minsk 200072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 4, pp. 539–545, July–August, 1998.     

Spectral luminescence properties of hydroporphyrazine metallo complexes

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.     

Characteristic features of carbazole phosphorescence quenching by benzophenone molecules in toluene at 77 K

We have studied the characteristic features of carbazole phosphorescence quenching by benzophenone in toluene at 77 K. We have shown that the decrease in the relative phosphorescence intensity for carbazole (energy donor) by a greater factor than we see for the relative change in its decay time is due to the fact that a change in the phosphorescence decay time occurs only for carbazole molecules participating in triplet-triplet energy transfer, while the substantial decrease in the phosphorescence intensity for carbazole with no change in the phosphorescence decay time is connected with quenching of its singlet states. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 554–556, July–August, 2006.     

Structure of the Absorption and Fluorescence Spectra of Solutions of Silico-Organic Polymers

The spectroscopic characteristics of new -linked polymers, whose main chain contains tetracoordinated silicon, acetylene groups, and 1,4-biphenyl or 2,7-fluorene, in chloroform have been investigated. It has been established that the spectral features of the absorption, fluorescence, fluorescence excitation, and fluorescence polarization spectra of these polymers are due to the inhomogeneous broadening of the electronic states of the centers of two types formed in the disordered polymer chain.     

Specific heat of LiB3O5 crystals in the temperature interval 80–300 K

The specific heat of LiB₃O₅ crystals is measured by adiabatic calorimetry. The experimental data on the specific heat are used to calculate the change in the thermodynamic functions (the entropy, enthalpy, and Gibbs free energy) and the Debye temperature Θ_D(T) of crystalline LiB₃O₅. Fiz. Tverd. Tela (St. Petersburg) 39, 624–625 (April 1997)     

Spectral characteristics of luminescence of solutions of complex molecules under conditions of electronic excitation transfer to a saturable acceptor in the case of inhomogeneous broadening of electronic energy levels

Spectral characteristics of solutions of complex molecules under conditions of inhomogeneous broadening of energy levels are considered in the case when the nonlinear dependence of the population of molecular states on the excitation intensity is determined not by saturation of molecular levels but by exchange of the electronic excitation energy with the environment. Calculations have shown that the dependence of the position of the fluorescence spectrum on the excitation frequency is nonmonotonic in solutions of the type and varies substantially with the excitation intensity. Belarusian State University, 4, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 164–168, March–April, 1997.     

Absorption and fluorescence spectra of hybrid silicon-organic materials in solutions and films

The spectroscopic characteristics of hybrid organic-inorganic films and solutions of ethoxysilicon-containing amidophosphate ligands in acetonitrile have been investigated. Inhomogeneous broadening of the absorption and fluorescence spectra which is characterized by the spectral dependence of the fluorescence and fluorescence excitation bands on the excitation and registration wavelength, respectively, is associated with the presence of a set of -(Si-O)_n- siloxane structures with various terminal fragments in both the films and solutions. The established general spectral rules are discussed with allowance for the characteristic features of the electronic structure of silicon-organic compounds containing an oxygen atom the unshared electron pair of which ensures the delocalization of the electron density over the siloxane chain.Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 71, No. 6, pp. 788–792, November–December, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Observation of the distorted form of Pd-porphin in single site spectra at low temperatures

Highly resolved phosphorescence and excitation of phosphorescence spectra for palladium porphin (PdP) in polycrystalline Shpol'skii matrices at liquid helium temperatures were recorded. Two non-interactive forms of PdP in the ground state have been identified. The energy splitting between the two forms amount up to 78 cm⁻¹ for PdP in an n-octane at 4.2 K. The short-wavelength spectral form is attributed to the structure, where the central Pd(II) ion is in plane of the porphyrin macrocycle, while the long-wavelength form is associated with the nonplanar saddle-type conformation of the PdP. The frequencies of the normal vibrations in the ground electronic state have been measured separately for both forms and the differences in the normal modes of two macrocycle conformations are discussed. The set of temperature activated bands in phosphorescence spectra were found. Analysis of phosphorescence spectra at elevated temperatures and excitation of phosphorescence spectra under direct excitation in the S₀→T₁ channel make possible the value of zero-field splitting of quasi-degenerate T_1,2 state for two forms to be determined. The splitting value in n-octane matrix amount to 40 and 57 cm⁻¹ for planar and nonplanar conformations of PdP, respectively.     

Inductive-resonant triplet-triplet annihilation in solid solutions of erythrosine

Experimental investigations of annihilation-induced delayed fluorescence and phosphorescence of frozen ethylene glycol solutions activated by erythrosine were carried out. It is found that the kinetics of the annihilation-induced delayed fluorescence is nonexponential in the initial stage, and approaches an exponential decay at later stages with the lifetime equal to half the triplet-state lifetime. It is shown that experimental data agree well with the theory proposed to describe triplet-triplet annihilation by an inductive-resonant mechanism in solid solutions of complex organic molecules. Belarusian State University, 4, F. Skorina Ave., Minsk, 2200050, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 5, pp. 629–632, September–October, 1997.     

Calibration of the R ruby fluorescence lines in the pressure range [0-1 GPa] and the temperature range [250-300 K]

Abstract

The pressure range [&1 GPa] and the temperature range [250–300 K] are commonly used in many science fields like biology, agro-chemistry, pharmacology, or geology. In this paper, the calibration of the ruby R lines of fluorescence is performed in these pressure and temperature ranges, using the melting curve of pure water. The linear shifts of ruby peaks are equal to ?0.140cm^?1/K and ?0.768cm^?1/kbar with R₁, and to ?0.137cm^?1/K and ?0.779 cm^?1/kbar with R₂. The accuracy of pressure measurements can be as good as ± 10MPa if the temperature is known with ±0.5 K. Such a precision is achieved if: (1) the position of each peak is determined using an inversion method; (2) daily shifts of the spectrometer are corrected before each acquisition; (3) peak positions of each ruby are known at ambient pressure and temperature.     

Interpretation of the soret band of porphyrins based on the polarization spectrum of N-methyltetraphenylporphin fluorescence

Low-temperature (77 K) absorption, fluorescence, and fluorescence-excitation spectra and the fluorescence polarization spectrum for N-methyl-meso-tetraphenylporphin (N-methyl-TPP) are measured. Based on the polarization spectrum the absorption spectrum in the visible region (a “generic” porphyrin spectrum) is interpreted. In particular, it is shown that the fifth absorption band (the “Longo band”) that manifests itself in some porphyrins is a Q_y(0–2) band and does not belong to the individual electron transition. Emphasis is placed on the region of the Soret band. It is inferred that at least two allowed electron transitions (G →B_x and G→B_y) polarized mutually perpendicularly manifect themselves in this region. The interpretation of the Soret band of porphyrins [2] that attributes this band to one electron transition G→B_x is thereby rejected. This interpretation is confirmed by computer modeling of the polarization spectrum. Special features of the experimental polarization spectrum are explained by a more developed vibrational structure and, possibly, a larger half-width of the B_x band than the half-width of the B_y band. The contribution of the states of intramolecular charge transfer to the formation of the Soret band is discussed. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 65–72, January–February, 1999.     

Spectral-Luminescent Properties and Electronic Structure of the Chlorin p 6 Derivatives with an Extended Conjugated Bond System

On the basis of spectral-luminescent investigations it is shown that the introduction of an additional hexatomic imidic ring into the chlorin p ₆ derivatives substantially shifts the absorption bands to the longwave spectral region but causes no decrease in the fluorescence quantum yield, i.e., it is not accompanied by an increase in the nonradiative deactivation rate of the excited singlet state S ₁. It follows from quantum-chemical calculations and also from the experimental data that the presence of this cycle in free bases results in the extension of the conjugated bond system and in the reduction of the singlet–triplet interval E(S ₁–T ₁) as compared to chlorin p ₆. In contrast to the majority of earlier investigated porphyrins and chlorins, the introduction of the central ion Zn into the chlorin p ₆ cycloimide derivative causes an increase in the quantum yield of fluorescence, lowering of the energy of the excited triplet state T ₁, and a noticeable (by 600 cm^–1) increase in the E(S ₁–T ₁) interval in comparison with the corresponding free bases. The data obtained are associated with the characteristic features of the extension of conjugated bond systems for the free bases of cycloimidoderivatives of chlorin p ₆ (22-membered cyclic polyene) and of their Zn complexes (20-membered cyclic polyene).     

Optical measurement of the speed of sound in air over the temperature range 300-650 K

Using laser-induced thermal acoustics (LITA), the speed of sound in room air (1 atm) is measured over the temperature range 300-650 K. Since the LITA apparatus maintains a fixed sound wavelength as temperature is varied, this temperature range simultaneously corresponds to a sound frequency range of 10-15 MHz. The data are compared to a published model and typically agree within 0.1%-0.4% at each of 21 temperatures.     

Evidence of neutral impurity scattering in mercury sulphide (α-HgS) in the temperature range 77–300 K correlation with chemical analysis

Five natural or synthetic trigonal HgS single crystals have been studied by transport experiments in the temperature range 77–300 K. The classical d.c. technique has been used to measure the Hall coefficient and the resistivity. The temperature dependence of the free carrier density in the conduction band associated to a chemical analysis have brought to light the presence of neutral donor impurities with a density much larger than the ionized ones, which has led us to consider the existence of neutral impurity scattering even at room temperature.A detailed study of the mobility has shown that, among the four possible and efficient scattering processes, (neutral impurities, ionized impurities, acoustical phonons and optical polar modes), the most efficient in the whole experimental temperature range is the neutral impurities one. However, at room temperature, the polar optical mode becomes comparable to the previous one. The agreement obtained between the experimental values of the mobility and the calculated ones by taking into account these four scattering modes is very good in the whole temperature range.So for the first time an explanation is given for the rather low value of the mobility in mercury sulphide. This explanation of the mobility behaviour is in good agreement with the results of the chemical analysis which shows in HgS-α the presence of impurities very much larger than that of the ionized impurities one.     

Spectroscopy of the a3Σu + state and the coupling to the X1Σg + state of K2

We report on high resolution Fourier-transform spectroscopy of fluorescence to the a³Σ_u ⁺ state induced by two-photon or two-step excitation from the X¹Σ_g ⁺ state to the 2³Π_g state in the molecule K₂. These spectroscopic data are combined with recent results of Feshbach resonances and two-color photoassociation spectra for deriving the potential curves of X¹Σ_g ⁺ and a³Σ_u ⁺ up to the asymptote. The precise relative position of the triplet levels with respect to the singlet levels was achieved by including the excitation energies from the X¹Σ_g ⁺ state to the 2³Π_g state and the frequencies of the fluorescence down to the a³Σ_u ⁺ state in the simultaneous fit of both potentials. The derived precise potential curves allow for reliable modeling of cold collisions of pairs of potassium atoms in their ²S ground state. Electronic supplementary material Supplementary Online Material     

Dependence of the spectroscopic properties of pentauranylfluoride crystals on temperature in the range from 4.2 to 40 K

Using the configuration interaction model, we investigate the dependence of the shape, half-width, and position of the phononless lines (PL) in absorption and luminescence spectra of K₃UO₂F₅ and Rb₃UO₂F₅ crystals in the region 4.2–40 K. It is established that a Stokes shift in combining electron states leads to a nonsymmetric distortion in the Gauss shape of thePL. The temperature broadening of the PL is mainly associated with a change in the population of the initial states of oscillators (of the ground state for absorption and the 1 st excited state for luminescence), while a shift in maxima of the PL is caused by the forbidden 1 st electron transitions in complex uranyl compounds and is determined by the nonlinear electron-phonon interaction. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 6, pp. 824–827, November–December, 1999.     

Fluorescence spectra of uranium induced by a linearly polarized laser light in a magnetic field

In this paper we reported the fluorescence spectra of U~(238) induced by a linearly polarized laser field in a magnetic field and offered a theoretical analysis. The consistence between the theoretical prediction and experimental results was satisfactory.     

Phosphorescence of molecules of polycyclic aromatic hydrocarbons in aqueous micellar solutions of sodium dodecylsulfate at room temperature

Deactivation of the excited states of pyrene, benzanthracene, and fluorene molecules in aqueous micellar solutions of sodium dodecylsufate is studied using steady and pulsed fluorimetry. Quenching of the singlet states of polyatomic hydrocarbons by thallium ions is considered. Effective, micellar, and biomolecular constants for the quenching rate are obtained. Phosphorescence constants for the aforementioned compounds are determined. Reasons behind the possibility of observing phosphorescence of polyaromatic compounds in micellar solutions at room temperature are ascertained. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 201–204, March–April, 1999.     

Study of the effects of Cr ions on Yb in Cr,Yb:YAG crystal

The absorption and fluorescence spectra of Cr,Yb:YAG crystal were measured. There are two absorption bands at 940 nm and 968 nm although the absorption coefficient is lower than that of the absorption peak of Yb:YAG superimposed in Cr:YAG absorption peak. The emission peak intensity is 4 times lower than that of Yb:YAG, which may be caused by the existence of the ground state absorption of Cr⁴⁺ which quenches the Yb³⁺ emission intensity. Although the emission peak of Cr,Yb:YAG is lower than that of Yb:YAG, there is an advantage of this crystal which combines the saturable absorber and gain medium into one and can be a self-Q switching laser crystal if Cr,Yb:YAG crystal is pumped with high energy power.