Thermalization after photoexcitation to the S2 state of <i>trans</i>-azobenzene in solution

Terazima, Masahide; Takezaki, Makoto; Yamaguchi, Shinji; Hirota, Noboru

doi:10.1063/1.476597

Cited by 41 publications

(33 citation statements)

References 35 publications

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“…87 Such an intuitive understanding of polarization and population gratings has enabled the method to be applied to a diverse range of systems. [84][85][86][87][88][89][90][91][92][93][94][95] Hence one might surmise that the origin of the signal decay when the experiment is applied to quantum dots relates to the selection rules for exciton photoexcitation and the circular-polarization character of the grating. However, it does not seem that the VHVH and VHHV experiments for QDs can be easily comprehended by considering the pump pulse sequence in isolation from the probe/analyzer.…”

Section: Transient Polarization Gratings and Quantum Dot Excitonmentioning

confidence: 99%

Exciton spin relaxation in quantum dots measured using ultrafast transient polarization grating spectroscopy

2006

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On the basis of quantum dot exciton states and selection rules for their excitation, a microscopic picture of a nonlinear optical spectroscopy that provides a direct probe of spin relaxation among quantum dot exciton states is described. Equations of motion which govern the evolution of the third order exciton population density are solved numerically to simulate the measured signals. It is shown how cross linearly-polarized pulse sequences in three-pulse transient grating experiments form a polarization grating that monitors the history of the bright exciton ͑F = ±1͒ spin states. Spin flips among those states lead to a decay of the grating, and consequently the diffracted probe signal. In the microscopic picture elucidated from the simulations, destructive interference between the third-order polarizations radiated by populations of excitons with flipped and conserved spin states causes the signal decay. The experiment permits the direct observation of the kinetics of exciton spin state flips in an isotropic ensemble of quantum dots. Such measurements are demonstrated for colloidal CdSe quantum dots at room temperature, and compared with results for a control experiment. The relationship between this experiment and a difference measurement based on circularly-polarized pump and probe pulses is established.

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Section: Transient Polarization Gratings and Quantum Dot Excitonmentioning

confidence: 99%

Exciton spin relaxation in quantum dots measured using ultrafast transient polarization grating spectroscopy

2006

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“…15 ps) evolution time observed earlier in a number of solvents 33,35,36,44,46,49,50 and associated with the intermolecular through-solvent energy transfer from azobenzene. The rise time of 0.24 ps can be assigned to the lifetime of the S 1 excited state and the characteristic time of S 1 f S 0 * internal conversion.…”

Section: Discussionmentioning

confidence: 91%

Ultrafast Dynamics of the Azobenzene−Coumarin Complex: Investigation of Cooling Dynamics Measured by an Integrated Molecular Thermometer

2005

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The energy dissipation mechanism from photoexcited azobenzene (Az) was studied by femtosecond time-resolved UV absorption spectroscopy using 7-amino-4-trifluoromethylcoumarin (ATC) as a probe. The distance between the probe molecule and Az was fixed by covalently linking them together through a rigid proline spacer. Picosecond dynamics in THF solutions were studied upon excitation into the S1 state by a 100 fs laser pulse at 480 nm. Transient absorption spectra obtained for Az-Pro-ATC combined the S1 state absorption and vibrationally excited ground-state absorption of ATC. Correction of the transient spectrum of Az-Pro-ATC for the S1 absorption provided the time-resolved absorption spectrum of the ATC hot band. Three major components were observed in the transient kinetics of Az-Pro-ATC vibrational cooling. It is proposed that in ca. 0.25 ps after the excitation, the S1 state of azobenzene decays to form an initial vibrationally excited nonthermalized ground state of Az-Pro-ATC that involves vibrational modes of both azobenzene and coumarin. This hot ground state decays in ca. 0.32 ps to the next, vibrationally equilibrated, transient state by redistributing the energy within the molecule. Subsequently, the latter state cools by transferring its energy to the closest solvent molecules in ca. 5 ps; then, the energy diffuses to the bulk solvent in 13 ps.

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“…In [20], at an angle between the interfering beams of 170 o (a grating period of 0.18 µm), hypersonic waves were excited in the bulk of ethanol at a frequency of 6.2 GHz. The results of [21], where the method of temporal shift of an acoustic pulse has been suggested and used for the first time to determine the time of thermolization of the energy accumulated in solutions of organic molecules, also point to the reality of carrying out the measurements mentioned above. In particular, in [21] ultrashort pulses were used and time delays of about 8 psec or less were measured at a grating period of about 0.6 µm.…”

Section: Introductionmentioning

confidence: 98%

“…The results of [21], where the method of temporal shift of an acoustic pulse has been suggested and used for the first time to determine the time of thermolization of the energy accumulated in solutions of organic molecules, also point to the reality of carrying out the measurements mentioned above. In particular, in [21] ultrashort pulses were used and time delays of about 8 psec or less were measured at a grating period of about 0.6 µm. This corresponds to an acoustic-oscillation period of 0.65 nsec and a frequency of 1.5 GHz.…”

Section: Introductionmentioning

confidence: 98%

Measurement of the normal thermal diffusivity of a dielectric film by a pulsed photoacoustic method

et al. 2004

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A method of determining the thermal diffusivity χ M of a thin film of a transparent dielectric in the direction normal to the surface has been developed. It is based on excitation of reflecting dynamic gratings. The effectiveness of the method is checked experimentally with the example of a thermally oxidized submicron SiO 2 film on a silicon substrate. The temperature dependence of χ M in the range 290-420 K is measured. The possibilities of setting up thermal measurements of films tens of nanometers thick and its problems are discussed.

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Thermalization after photoexcitation to the S2 state of trans-azobenzene in solution

Cited by 41 publications

References 35 publications

Exciton spin relaxation in quantum dots measured using ultrafast transient polarization grating spectroscopy

Exciton spin relaxation in quantum dots measured using ultrafast transient polarization grating spectroscopy

Ultrafast Dynamics of the Azobenzene−Coumarin Complex: Investigation of Cooling Dynamics Measured by an Integrated Molecular Thermometer

Measurement of the normal thermal diffusivity of a dielectric film by a pulsed photoacoustic method

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