The fluorescence spectrum of HCN (A≈1 A′' → X≈1 Σ+) using ArF laser excitation

The fluorescence spectrum of HCN A≈(¹A′') → X≈(¹Σ⁺) is reported using a tuned ArF laser as the excitation source. Assignments for the fluorescence spectra from two upper state vibrational levels are given. Franck—Condon factors for the absorption and fluorescence spectra are calculated. A laser-induced fluorescence spectrum is given which agrees with published absorption spectra of HCN.     

Two-photon and multi-photon excitation of naphthalene in the vapor phase,studied by excitation and fluorescence spectra

Naphthalene vapor is irradiated by μsec dye laser pulses of 150 kW peak power and a spectral bandwidth of 0.3 nm. A two-photon excitation spectrum is detected by monitoring the near UV fluorescence as a function of laser wavelength which is tuned between 570 and 610 nm. The fluorescence obtained by irradiation into the strongest band of the two-photon spectrum could be spectroscopically resolved using a bandwidth of 80 cm^?1. The spectrum exhibits vibrational structure which lies on a strong non-resolved background. From information in both spectra it can be definitely concluded that vibronic levels of B_3u × b_3u species in the lowest singlet state are predominantly excited in a two-photon process. The non-resolved background in the fluorescence spectrum is attributed to subsequent excitation of the two-photon state by a third photon. Further stepwise excitation in the strong radiation field of the laser is also taken into account.     

The laser-induced fluorescence spectrum of chromyl fluoride (chromium dioxidedifluoride) in a seeded molecular beam

We habe obtained part of the laser-induced fluorescence spectrum of chromyl fluoride in a free jet expansion at an instrumental resolution of better than 0.001 cm^?1. This spectrum (together with that of the dispersed fluorescence) allows the identification of the (0,0) band or the absorption spectrum and of several progressions in the lowest bending frequency.     

The electronic emission spectrum of benzaldehyde vapour

The electronic emission spectrum of benzaldehyde vapour excited in a discharge consists mainly of ã³A″-X?¹A′ phosphorescence but also contains some weak ùA″-X?¹A′ fluorescence. The spectrum has been photographed under high resolution with a view to establishing which a″ vibrations are active in the ã-X? system. We have shown, with the help of rotational band contours, that the vibration in which the substituent as a whole moves out-of-plane is weakly active and that the substituent torsional vibration is more weakly active. These are the only a″ vibrations which are active with sufficient intensity to be observed in the spectrum.In the Ã-X? fluorescence an a″ wagging vibration of the hhydrogen atoms of the phenyl ring is moderately strongly active, as is the corresponding excited state vibration in the Ã-X? absorption system     

Studies on Thermodynamics Features of the Interaction between Imidacloprid and Bovine Serum Albumin

At different temperatures, the interactions between imidacloprid （IMI） and bovine serum albumin （BSA） were investigated with a fluorescence quenching spectrum, a synchronous fluorescence spectrum, a three-dimensional fluorescence spectrum and an ultraviolet-visible spectrum. The average values of bonding constants （KLB： 3.424 × 10^4 L,mol^-1）, thermodynamic parameters （△H： 5.188 kJ,mol^-1, △G^（○—）：-26.36 kJ,mol^-1, △S： 103.9 J,K^-1,mol^-1） and the numbers of bonding sites （n： 1.156） could be obtained through Stern-Volmer, Lineweaver-Burk and ther- modynamic equations. It was shown that the fluorescence of BSA could be quenched for its reactions with IMI to form a certain kind of new compound. The quenching belonged to a static fluorescence quenching, with a non-radiation energy transfer happening within a single molecule. The thermodynamic parameters agree with △H〉 0, △S〉0 and△G^（○-）〈0, suggesting that the binding power between IMI and BSA should be mainly a hydrophobic interaction.     

Fluorescence turn-on chemosensor for Hg<Superscript>2+</Superscript> based on a rhodamine derivative and its application in bioimaging

A fluorescence turn-on chemosensor based on rhodamine B derivative (FD10) has been developed as a highly sensitive chemosensor for Hg²⁺. A prominent fluorescence enhancement was measured in the presence of Hg²⁺, which was in agreement with the changes in the absorption spectrum. Furthermore, by means of laser scanning fluorescence microscopy experiments, it was demonstrated that FD10 was cell-permeable and could be used as a fluorescent probe for monitoring Hg²⁺ in living cells. Supported by the National Natural Science Foundation of China (Grant No. 20801015) and Shanghai Leading Academic Discipline Project (Grant No. B108)     

Self-absorption effects on alpha-induced atmospheric nitrogen fluorescence yield

Nitrogen fluorescence induced by radiation can be used to detect the presence of radioactive contamination in the environment. Contamination quantification from the fluorescence signal requires: the source’s effective alpha spectrum; the specific radiation quantum fluorescence efficiency; optical attenuation length in air of the fluorescence signal; the absolute throughput and quantum efficiency of the optical instrumentation; calibration of the instrumentation; and radiation transport modeling of the “effective” array exposure rate given the alpha particle spectrum. Field testing conducted on optical instrumentation measured the nitrogen fluorescence yield generated by ²⁴¹Am alpha emissions. Laboratory studies of ²⁴¹Am via alpha spectrometry determined whether the presence of solids on source surfaces produced sufficient self-absorption to decrease fluorescence. Results from the laboratory studies provided correction to the effective alpha-source activity values in a model of the earlier optical-sensor field measurements, and determined the air fluorescence efficiency of alpha particles generated by the ²⁴¹Am sources used in the field experiments.     

Lyman-α excitation spectra in the photodissociation of the doubly excited states of H2

A Lyman-α excitation spectrum has been observed using synchrotron radiation in the energy region corresponding to the double electron excitation of H₂. There exist in the spectrum three thresholds at 26.6±0.5 eV, 29.2±0.7 eV and 30.9±0.6 eV, and a dip at 34.1±0.5 eV. A Lyman-α excitation spectrum in the energy region corresponding to the single electron excitation has been also observed using a detection system which works as a band pass filter for detecting of Lyman-α fluorescence. The cross section of Lyman-α fluorescence in the photodissociation of the doubly excited states is very small, e.g., in the order of 10^?20 cm² at 30 eV, in comparison with that from the single electron excitation.     

Electronic emission spectrum of p-fluorobenzaldehyde vapour

The high resolution electronic emission spectrum of p-fluorobenzaldehyde vapour excited in a discharge is reported for the first time. The spectrum consists of both the ã³A″?X?¹A′ phosphorescence and the ùA″?X?¹A′ fluorescence bands. Whereas all the eleven out-of-plane vibrations appear in the fluorescence spectrum, only the φ-CHO torsional vibration and the φ-CHO wagging vibration appear in the phosphorescence. A total of thirty ground state vibrational frequencies out of the thirty-six possible fundamentals have been obtained from the emission bands. Both the fluorescence and the phosphorescence emission spectra of p-fluorobenzaldehyde are very similar to those of benzaldehyde itself. This shows that the electronic transitions are not very sensitive to the substitution of fluorine at the para position of benzaldehyde.     

Electroluminescence of a bichromophoric molecule with a benzoxyazolylcoumarin and carbazole moiety

The electroluminescent properties of a bichromophoric molecule in which a benzoxyazolylcoumarin and carbazole moiety is combined with 1,2-ethylene linkage, i.e. 3-(2-benzoxyazolyl)-7-[2-(9-carbazolyl)ethoxy]-coumarin (CmCz), were investigated. CmCz exhibits fluorescence of different colors in a solid state and solution. Two types of device were made. One consisted of a vacuum vapor-deposited film of CmCz as an emission layer to utilize fluorescence in the solid state; the second consisted of a spin-cast film doped with CmCz as an emission material to utilize fluorescence in the solution. The device with a vapor-deposited CmCz film between electrodes shows a green emission with a luminance of less than 10⁻² cd/m². The multiple layer device in which the CmCz film was sandwiched between a hole transport layer and electron transport layer showed a green emission whose spectrum is identical to the photoluminescent spectrum in the vapor-deposited CmCz film. A maximum luminance of the multiple layer device is about 5000 cd/m². On the other hand, the devices consisting of a spin-cast film containing a hole transport material, an electron transport material and CmCz showed a blue emission whose spectra are identical to the photoluminescent spectrum of CmCz in chloroform. Luminance of these devices is over 100 cd/m². © 1997 John Wiley & Sons, Ltd.     

Rotational effects on the quantum yield and lifetime of the slow component of fluorescence from s-triazine

The fluorescence quantum yield and lifetime of the slow component of fluorescence obtained along the rotational contour of the 6¹₀ and 6²₀ absorption bands of s-triazine at low pressure show a marked variation. For each band, the quantum-yield spectrum shows a sharp peak at the Q-branch edge, the lifetime spectrum exhibits a valley at the same position.     

1B2u1A1g fluorescence from benzene produced by electron impact (30–1000 eV)

The ¹B_2u → ¹A_1g fluorescence resulting from electron impact (30–1000 eV) on benzene has been studied in the pressure range 10^?4 ?2 × 10^?3 torr. The fluorescence spectrum is compared with the spectrum obtained by other methods. The energy dependence of the absolute emission cross section indicates a small probability for internal conversion from higher singlet states to the ¹B_2u state.     

聚酯聚醚嵌段共聚物与1,4-二咔唑环丁烷在激发态及基态的相互作用

<正> 聚酯聚醚嵌段共聚物具有十分良好的物理和机械性能,能加工成橡胶、纤维、塑料胶粘剂等,近年来也有作为医用高分子材料的报道。所以对聚酯聚醚嵌段共聚物的研究十分活跃。然而,有关其光物理性质的研究还很少见。本文报道了混合聚醚-聚酯嵌段共聚物(MPEE)与反式1,4-二咔唑环丁烷(1,4-DCC)在激发态和基态下的相互络合作用。结果表明,MPEE可以猝灭1,4-DCC的荧光,同时形成激基复合物。在分散     

Studies on Intramolecular Charge Transfer Fluorescence Probe and DNA Binding Characteristics

An intramolecular charge transfer fluorescence probe of 4′-N,N-dimethylamino-4-amino-chalcone(DMAC) exhibits characteristics clearly correlated with the polarity of solvents. The interaction of this fluorescence probe with calf thymus DNA has been investigated. Generally, DMAC bound to DNA shows marked changes in fluorescence and absorbance properties compared to the spectral characteristics of the free form in solution phase. In the presence of DNA the fluorescence intensity of DMAC is greatly increased with a large bathochromic shift of excitation and emission wavelengths. A hypochromism in absorption spectrum was also observed. The absorption and fluorescence spectra, salt concentration effect, and KI quenching experiments demonstrate that DMAC molecule as an intercalator is inserted into the base-stacking domain of DNA double helix, and the interaction of the nucleobases with DMAC molecule causes the increase of fluorescence intensity and hypochromism in absorption spectrum. The intrinsic binding constant and the binding site number were estimated to be 7.04 × 10⁶ mol L⁻¹ in base pairs and 0.065, respectively. The I/I₀ vs DNA concentration plot shows a linear range covering 1.98 × 10⁻⁶ to 2.08 × 10⁻⁴ mol L⁻¹ in base pairs which can be used for determining DNA with a detection limit of 6.0 × 10⁻⁷ mol L⁻¹ in base pairs (0.6 μg ml⁻¹).     

Effects of Si−Al composition on the fluorescence spectra of 1-naphthol during the sol-gel-xerogel transitions

A systematic study has been carried out on the characteristic changes in the fluorescence spectra of 1-naphthol doped in the sol-gel-xerogel transition systems comprised of tetraethyl orthosilicate and diisobutoxyaluminium triethylsilicate catalyzed by a small amount of HCl, NH₄OH, as well as under uncatalyzed conditions. In the systems containing large amounts of silicon, the fluorescence of 1-naphthol shifts to the red (a predominant emission from the ¹L_a state) during the first stage of the reaction. This red shift indicates an increase in the polarity of the matrix surrounding 1-naphthol. In the second stage of the reaction, the spectrum shifts to the blue (a predominant emission from the ¹L_b state), reflecting an increase in the micro-viscosity around 1-naphthol. In the systems containing relatively large amounts of aluminum, however, the spectrum just after mixing shows a larger red shift than that originating from the ¹L₂ emission. This large red-shifted fluorescence reflects the formation of a complex between 1-naphthol and the −O−Al−O−Si−O-network. The spectrum then shifted to the blue. The spectral behaviours observed indicate that there is a large and dynamic molecular-level change in the physicochemical properties of the matrix surrounding the 1-naphthol molecules during the sol-gel-xerogel transitions of the systems while the gelation phenomenon reflects macroscopic inflexibility although it is completely different from the restriction of movement at the molecular level.     

Synthesis and Verification of 9,10-Diphenylanthracene and Its Utility as a Fluorescer in a Peroxyoxalate Chemiluminescence System. An Organic Laboratory Project Integrating Synthesis with Fluorescence and Chemiluminescence

A project for the organic laboratory integrating the organic synthesis of 9,10-diphenylanthracene with fluorescence and chemiluminescence is described. The fluorescent compound is synthesized from anthraquinone by reaction with phenyllithium and subsequent hydrolysis and reduction with KI and NaH₂PO₂ in acetic acid. The structure of the product is verified by its melting point and by IR, ¹H NMR, and fluorescence spectroscopy. A peroxyoxalate chemiluminescent reaction using bis(2-butoxycarbonyl-3,4,6-trichlorophenyl) oxalate and hydrogen peroxide as the energy source is tested. The chemiluminescence emittance spectrum of the prepared diphenylanthracene is found to be essentially identical to that of the fluorescence spectrum of the same compound. Finally, the kinetics of the chemiluminescent reactions using different intensity-modifiers are monitored by measuring intensity-versus-time decay curves.     

Binding mode of proflavine to DNA probed by polarized light spectroscopy

It is well known that proflavine binds to DNA. Here we investigate the binding mode of proflavine to native DNA using absorption, circular dichroism (CD), and linear dichroism (LD) spectroscopy as well as by fluorescence techniques. The observed changes of proflavine upon complexation with DNA can be summarized as a red shift and hypochromism in the absorption spectrum. The negative LD^r in the proflavine absorption region has a magnitude comparable to or larger than that of the DNA absorption region, confirming the intercalative binding mode of proflavine to DNA. Saturation of the LD spectrum in the proflavine absorption region at R = 0.25 and a decrease in the fluorescence intensity provide further evidence of intercalation. Furthermore, the coupling of electric transition of intercalated proflavine is observed. Although proflavine has been reported to position itself along the DNA stem at high [proflavine]/[DNA base] ratios, the spectral characteristics, which include a clear isosbestic point in the absorption spectrum and proportionality in the LD magnitude in the proflavine absorption region, do not show any possibility of exterior binding.     

EXCITED-STATE PROPERTIES OF DNA METHYLATED AT THE NV7 POSITION OF GUANINE AND ITS FREE FLUOROPHORE AT ROOM TEMPERATURE

The room-temperature optical properties of calf thymus DNA, with about 75% of its guanine residues methylated at position N-7, are compared with those of 7-methyl GMP which has the same fluorophore. The fluorescence spectrum of the methylated guanine residues depends strongly on the excitation wavelength, shifting to the blue as the wavelength increases. The fluorescence quantum yield, corrected for the contribution to absorption by the other virtually nonfluorescent residues, exhibits a pronounced drop at long excitation wavelengths relative to that for excitation at 265 nm. The degree of fluorescence polarization exhibits a weak dependence on the excitation and emission wavelengths. For 7-methyl GMP, the fluorescence spectrum is very weakly dependent on the excitation wavelength and its fluorescence quantum yield shows a moderate increase at long wavelengths. The degree of fluorescence polarization increases with increasing excitation wavelength particularly when monitoring the emission in the short wavelength region of the fluorescence spectrum. A pronounced drop of unknown origin is observed when exciting at 265 nm, which is not observed for methylated DNA. The methylated DNA data are interpreted in terms of a combination of (i) a heterogeneous environment of the methylated guanine residues, which results from sequence-dependent stacking interactions, and (ii) transfer of excitation energy from the other residues to the fluorescing methylated guanine residues. From the values of the quantum yields and those of the decay times, which we have recently reported (Georghiou et al., 1985), the following values are obtained for the radiative, k_t, and the sum of the nonradiative, σk₁, rate constants for deexcitation of the excited states of methylated DNA and its free fluorophore: 1.6 × 10⁸ s^-1 7 × 10⁷ s^-1 and 5 × 10¹⁰ s^-lvs 6 × 10⁹ s^-1. Because of energy transfer from the other residues. the k_f value for the methylated guanine residues is overestimated but their σk₁, value is not affected significantly and is by about an order of magnitude larger than that for 7-methyl GMP, apparently because of stacking interactions.     

Effects of Triton X-100 on Properties of Hemoglobin and Controlled Release of Drug in Hemoglobin/Ribavirin/H2O System

Effects of Triton X-100 on the properties of hemoglobin (Hb) and on the controlled release of ribavirin were studied using the methods of UV-Vis spectrum, fluorescence spectrum, zeta potential, conductivity, high-performance liquid chromatographic (HPLC), and image morphology in Hb/ribavirin/H₂O system. With the increase of concentration of Triton X-100 in the system, the intrinsic fluorescence intensity, synchronous fluorescence intensity, fluorescence polarization, zeta potential, and morphology of Hb all changed gradually, and the ribavirin located on the Hb surface was dissociated and released out. When the concentration of Triton X-100 was higher than 1×10⁻⁵ mol·L⁻¹, the stronger interaction of Triton X-100 with Hb was predominant. Hb was unfolded and denaturized. A little Triton X-100 can protect Hb from the effects of ribavirin.     

Anomalous fluorescence of aceanthrylene: An example of second excited state emission (S2 → S0)

An anomalous fluorescence with a quantum yield of 0.017 near 24000 cm^?1 is detected from hexane solutions of aceanthrylene. Excitation and synchronous scan spectra verify that the second excited state with a lifetime of 4.3 ns is the source of the fluorescence. The absorption spectrum is simulated by PPP SCF CI computations.