Resonant light scattering and luminescence in multimode vibronic systems: time‐dependent representation

Hizhnyakov, V.; Tehver, I.

doi:10.1002/jrs.714

Cited by 4 publications

(3 citation statements)

References 15 publications

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“…Therefore the expression “selective scattering” is synonymous with “resonance light scattering.” Resonance light scattering has been widely observed in Raman scattering. However the resonance effects are equally applicable to luminescence and Rayleigh scattering [ 22 ]. Resonance scattering should be minimal in the case of mixtures of microspheres and chromophores since scattering from the individual chromophores is negligible compared to scattering from the microspheres.…”

Section: Discussionmentioning

confidence: 99%

Measurement of Absorption and Scattering With an Integrating Sphere Detector: Application to Microalgae

Gaigalas

Wang

2009

J.Res Natl.Ins. Stand.Technol.

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A spectrometer with an integrating sphere (IS) detector was used to measure the absorbance due to scattering and absorption. Analysis of the measurement process showed that two measurements of the absorbance, one with the cuvette placed in the normal spectrometer position, and the second with the cuvette placed next to the entrance aperture of the IS detector, provide enough information to separate the contributions from scattering and molecular absorption. Measurements were carried out with mixtures of microsphere and chromophore solutions. Two cases were examined: microspheres suspended in an aqueous fluorescein solution, and microspheres suspended in an aqueous holmium oxide solution. In both cases, the proposed measurement model gave results which were in good agreement with the expected response. Measurements on microalgae suspensions yielded a molecular absorption contribution and a scattering contribution. The scattering contribution had significant spectral structure which was inversely related to the molecular absorption contribution. The absorption and scattering contributions may provide independent information on the status of chlorophyll molecules and the structure of chloroplasts in microalgae.

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Section: Discussionmentioning

confidence: 99%

Measurement of Absorption and Scattering With an Integrating Sphere Detector: Application to Microalgae

Gaigalas

Wang

2009

J.Res Natl.Ins. Stand.Technol.

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“…This method allows one to calculate the Fourier-transform of the optical spectrum via the Fourier-transforms of the one-and twophonon amplitudes of the resonance Raman scattering. Previously this method was used for investigation of the effect of mode mixing in the resonant Raman scattering [11][12].…”

Section: Optical Transition To a State With Soft Phonon Dynamicsmentioning

confidence: 99%

Multiphonon processes in impurity centres: nonperturbative theory

Hizhnyakov

Boltrushko

Kaasik

et al. 2005

Physica Status Solidi (a)

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A nonperturbative theory of the multiphonon relaxation of a strongly excited local vibration is developed. It is found that for a high initial level, the relaxation first accelerates in time, and later starts to slow down. The experimental evidence of such a non-monotonous relaxation is given by the hot luminescence in solid Xe. A theory of optical transitions in a center with strongly reduced local springs in the final electronic state is also developed. In this case a resonant increase of the local density of states of low-frequency phonons takes place, and a low frequency pseudo-local mode emerges. Appearance of such a mode in the final state means that a strong mode mixing takes place at the transition. This results in strong increase of the mean number of created low-frequency phonons. As a consequence, the zero-phonon transition practically disappears and the long-wave part of the phonon sideband is strongly enhanced, resulting in formation of so-called lambda-shaped spectrum. Multiphonon relaxation of local modePhysical processes in solids usually involve the relaxation of the vibrational energy. For example, optical excitation of F-centers or other centers in ionic crystals and self-trapped excitons usually leads to excitation of strong vibrations. In CARS experiments one usually excites strong long-wave coherent vibration, which decays via multiphonon anharmonic interaction into other phonons. Laser methods allow one to achieve also direct excitation of non-coherent vibrations of impurity molecules in crystals. The subsequent processes are essentially determined by the relaxation of these vibrations. The vibrational quanta of light molecules may exceed many times the maximal energy of phonons. In such a case the vibrational relaxation takes place as a multiphonon emission. Usually this process is considered in the frames of the perturbation theory, by applying the Fermi Golden Rule [1 -5]. However, this theory works only if the energy of the mode is small. Here we apply another method [6 -7], which works for the large energy of the mode, supposing that the relaxation rate remains less than the frequency ω l of the mode.In [6][7] it is taken into account that a strongly excited mode can be considered classically. Then the mode causes a perturbation of phonons which is quasi-periodical in time. The Coleman theorem [8] reads that the zero-point state and the operators of bosons interacting with a classical field are not invariant with respect to the transformation which changes the classical field. It means that the transformed destruction operators are not the zero operators for the initial zero-point state. This corresponds to the fact that classical field which changes in time leads to emission of phonons.

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“…Here we are considering a case when the optical transition takes place between the electronic states with hard and soft local phonon dynamics. To find the spectrum in this case we use the method [1], which allows one to express the Fourier transform of the optical spectrum via the Fourier transforms of the one-and two-phonon amplitudes of the resonance Raman scattering [2,3]. In the case under consideration the mean phonon frequency of the vibrations of the centre is strongly reduced, which allows one to use, as a small parameter of the theory, the ratio of the mean frequencies in the final and the initial states.…”

Section: Introductionmentioning

confidence: 99%

Optical spectra of systems with nearly unstable excited states: modulated lambda-shaped spectra

Hizhnyakov

Benedek

Tehver

et al. 2006

Journal of Non-Crystalline Solids

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Resonant light scattering and luminescence in multimode vibronic systems: time‐dependent representation

Cited by 4 publications

References 15 publications

Measurement of Absorption and Scattering With an Integrating Sphere Detector: Application to Microalgae

Measurement of Absorption and Scattering With an Integrating Sphere Detector: Application to Microalgae

Multiphonon processes in impurity centres: nonperturbative theory

Optical spectra of systems with nearly unstable excited states: modulated lambda-shaped spectra

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