Different Real and Imaginary Components of the Resonant Third-Order Polarization Revealed by Optical Heterodyne Detected Transient Grating Spectroscopic Studies of Crystal Violet:  Model and Experiment

Xu, Qing‐Hua; Ma, Ying‐Zhong; Fleming, Graham R.

doi:10.1021/jp014714n

Cited by 22 publications

(45 citation statements)

References 44 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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“…In order to scale the response functions according to the population kinetics, each response function has to be separated into a nuclear and an electronic population kinetic component (Yan and Mukamel 1991;Xu et al 1999;Xu and Fleming 2001;Stenger et al 2002;Xu et al 2002;Jimenez et al 2004;Nibbering and Elsaesser 2004). For example, R 2 is scaled as a function of the population time T according to the corresponding kinetics of the S 2 state with the decay rate C. In this case, we can write R 2 ¼ R 0 2 exp½ÀCT, where R 0 2 represents the nuclear dynamics; the population kinetic component exp[-CT] has been separated.…”

Section: Numerical Calculationmentioning

confidence: 99%

Four-wave mixing signals from β-carotene and its n = 15 homologue

et al. 2007

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The third-order nonlinear optical responses of beta-carotene and its homologue having a conjugation-double bond n = 15 have been investigated using sub-20 fs ultra-short optical pulses in order to clarify the dissipation processes of excess energy. Using the four-wave mixing spectroscopy, we observed a clear coherent oscillation with a period of a few tens of femtoseconds. The spectral density of these molecules was estimated that allowed the theoretical linear and nonlinear optical signals to be directly compared with the experimental data. Calculations based on the Brownian oscillator model were performed under the impulsive excitation limit. We show that the memory of the vibronic coherence generated upon the excitation into the S(2) state is lost via the relaxation process including the S(1) state. The vibronic decoherence lifetime of the system was estimated to be 1 ps, which is about 5 times larger than the life time of the S(2) state ( approximately 150 fs) determined in previous studies. The role of coherence and the efficient energy transfer in the light-harvesting antenna complexes are discussed.

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“…Acetonitrile is transparent at 405 nm, and therefore, the signal is predominantly dispersive. 42,46 Dividing eq 10 by ˆ4(ω t ) and exp(-iω t τ j 4 ) and then adding 4 (ω t ) to ψ(ω t ) gives the heterodyne detected EFR-TG signal field…”

Section: Principles Of Spectroscopic Methodsmentioning

confidence: 99%

Coherent Electronic and Nuclear Dynamics for Charge Transfer in 1-Ethyl-4-(carbomethoxy)pyridinium Iodide

2006

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Although polaronic interactions and states abound in charge transfer processes and reactions, quantitative and separable determination of electronic and nuclear relaxation is still challenging. The present paper employs the amplitudes, polarizations, and phases of four-wave mixing signals to obtain unique dynamical information on relaxation processes following photoinduced charge transfer between iodide and 1-ethyl-4-(carbomethoxy)-pyridinium ions. Pump-probe signal amplitudes reveal the coherent coupling of an underdamped 115 cm -1 nuclear mode to the charge transfer excitation. Assignments of this recurrence to intramolecular vibrational modes of the acceptor and to modulation of the intermolecular donor-acceptor distance are discussed on the basis of a high-level density functional theory normal-mode analysis and previously observed wave packet dynamics of solvated molecular iodine. Nuclear relaxation of the acceptor induces sub-picosecond decay of the pump-probe polarization anisotropy from an initial value of 0.4 to an asymptotic value of -0.05. Electronic structure calculations suggest that relaxation along the torsional coordinate of the ethyl group is the origin of the anisotropy decay. Electric-field-resolved transient grating (EFR-TG) signal fields are obtained by spectral interferometry with a diffractive optic based interferometer. These measurements show that the signal phase and amplitude possess similar dynamics. Model calculations are used to demonstrate how the EFR-TG signal phase yields unique information on transient material resonances located outside the laser pulse spectrum. This effect can be rationalized in that the real and imaginary parts of the nonlinear polarization are related by the Kramers-Kronig transformation, which allows the dispersive component of the polarization response to exhibit spectral sensitivity over a larger frequency range than that defined by the absorption bandwidth.

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Different Real and Imaginary Components of the Resonant Third-Order Polarization Revealed by Optical Heterodyne Detected Transient Grating Spectroscopic Studies of Crystal Violet: Model and Experiment

Cited by 22 publications

References 44 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

Four-wave mixing signals from β-carotene and its n = 15 homologue

Coherent Electronic and Nuclear Dynamics for Charge Transfer in 1-Ethyl-4-(carbomethoxy)pyridinium Iodide

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