Real time-dependence of photodissociation and continuum Raman experiments

Shapiro, Moshe

doi:10.1021/j100131a005

Cited by 59 publications

(39 citation statements)

References 9 publications

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“…(13) The excited wave packet is seen to be a sum of replicas launched by all the delta pulses up till time t, evolving according to the excited state Hamiltonian H x [14,15]. Written in differential form…”

Section: Theory Of "Random" and Coherent Wave Packet Dynamicsmentioning

confidence: 99%

Nature of Quantum States Created by One Photon Absorption: Pulsed Coherent vs Pulsed Incoherent Light

Han¹,

Shapiro²,

Brumer

2013

J. Phys. Chem. A

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We analyze electronically excited nuclear wave functions and their coherence when subjecting a molecule to the action of natural, pulsed incoherent solar-like light, and to that of ultrashort coherent light assumed to have the same center frequencies and spectral bandwidths. Specifically, we compute the spatio-temporal dependence of the excited wave packets and their electronic coherence for these two types of light sources, on different electronic potential energy surfaces. The resultant excited state wave functions are shown to be qualitatively different, reflecting the light source from which they originated. In addition, electronic coherence is found to decay significantly faster for incoherent light than for coherent ultrafast excitation, for both continuum and bound wave packets. These results confirm that the dynamics observed in studies using ultrashort coherent pulses are not relevant to naturally occurring solar-induced processes such as photosynthesis and vision.

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Section: Theory Of "Random" and Coherent Wave Packet Dynamicsmentioning

confidence: 99%

Nature of Quantum States Created by One Photon Absorption: Pulsed Coherent vs Pulsed Incoherent Light

Han¹,

Shapiro²,

Brumer

2013

J. Phys. Chem. A

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“…In each step we use firstorder perturbation theory. According to this procedure, the preparation coefficients are given aslo For a Gaussian pulse, where we parametrize e(w) for complex frequencies as -a2y2/4j (11) sgn(t? ~X P [ W J )~I Wsgn(t?…”

Section: Review Of the Theory Of Continuum Secondary Emission With Comentioning

confidence: 99%

Theory of emission from dissociating states: the methyl iodide excitation spectrum

Shapiro¹

1993

J. Phys. Chem.

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The uniform theory of photoemission of a dissociating molecule excited by a laser pulse is developed. It is shown that transient effects lead to the appearance of additional terms, not included in the Kramers-Heisenberg formula. The role of "true" Raman scattering vs "resonance fluorescence" in contributing to the observed signal is elucidated. It is shown that the relative importance of these two processes is strongly dependent on the pulse parameters and the radiative lifetimes. "True" Raman is shown to dominate a t very short times, during the rise of the pulse. At longer times resonance fluorescence sets in and dominates the observed signal. Computations based on the above theory of the time-averaged excitation-emission spectrum (the emission signal as a function of the excitation wavelength) of CH3I with real nanosecond pulses are presented. The present study explains the rich structure observed experimentally and points out ways of translating this structure to "real-time" information.

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Section: Introductionmentioning

confidence: 99%

“…The details of the excitation process play an important role also in other experiments like real-time dependence of photodissociation and other processes recently studied in the framework of coherent control (see [9,10] and 2 is created. During the creation, it begins to propagate on the potential energy surface of the intermediate electronic state and, simultaneously, decays to the final electronic states by emitting particles of energy E. The decayed components propagate on the surfaces of the final states and may interfere with new contributions added continously from the decaying state.…”

Section: Introductionmentioning

confidence: 99%

“…Including the excitation process, the Hamiltonian, which describes the whole system, becomes time-dependent. Thus, the natural way to take the excitation into account is the time-dependent picture.The details of the excitation process play an important role also in other experiments like real-time dependence of photodissociation and other processes recently studied in the framework of coherent control (see [9,10] and …”

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Competition between excitation and electronic decay of short-lived molecular states

Pahl¹,

Meyer²,

Cederbaum³

1996

Z Phys D - Atoms, Molecules and Clusters

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The nuclear dynamics accompanying the excitation to and the subsequent decay of an electronic state is discussed. Particular attention is paid to cases, in which the whole process cannot be divided into two steps (excitation and decay) since the excitation and the decay times are of the same order of magnitude. The recently introduced time-dependent formulation of the theory describing the wave packets' dynamics is extended to include the excitation process. The wave packets can be related to the intensity of the emitted particles. Most of the resulting integrals can actually be performed by employing eigenstates of the Hamiltonians corresponding to the involved potential energy surfaces. This leads to the so called ''timeindependent'' formulation of the theory. Computational details of the implementation of the corresponding ''timedependent'' and ''time-independent'' methods are presented. Illustrative applications are given to illuminate both the influence of the excitation process and the lifetime of the decaying state. It emerges that the intuitive interpretation of the spectra (within the above two step model) may fail. Insight into the process is gained by studying the evolution of the spectra as a function of time. The appearance of ''atomic lines'' due to dissociative decaying and final states is investigated in some detail.PACS: 33.80.!b; 32.80.Hd; 42.55.Vc I IntroductionThe spectroscopic methods which involve the appearance of an excited decaying electronic state can roughly be divided into absorption or emission spectroscopies. In the first class the excitation process, i.e. the transition between the initial and the intermediate, decaying state is observed. Examples are conventional optical absorption spectroscopies and electron energy loss spectroscopy (EELS). In the emission spectroscopies the decay of the excited electronic state is studied. Under these spectroscopies come methods like X-ray emission spectroscopy (XES), Auger electron spectroscopy (AES) or the autoionization of coreexcited states.This classification is useful if the effects of nuclear dynamics on the detected spectra are considered. In absorption spectroscopies the nuclear dynamics leads in combination with the finite lifetime of the excited state only to a broadening of the observed bands. In emission spectroscopies, however, additional effects due to interference phenomena may occur. Apart from band broadening the bands can be energetically shifted and asymmetric band forms may be introduced [1, 2]. These effects are the strongest if the lifetime of the decaying state is in the range of the typical times of internal vibrations in this state.If the excitation time is of the same order-of-magnitude as both the lifetime of the decaying state and the typical time of internal vibrations, further effects in the spectra may appear. Then, the observed spectra are also influenced by the duration and other details of the excitation. In these cases the excitation process cannot be regarded as an instantaneous process, which can be separated...

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Real time-dependence of photodissociation and continuum Raman experiments

Cited by 59 publications

References 9 publications

Nature of Quantum States Created by One Photon Absorption: Pulsed Coherent vs Pulsed Incoherent Light

Nature of Quantum States Created by One Photon Absorption: Pulsed Coherent vs Pulsed Incoherent Light

Theory of emission from dissociating states: the methyl iodide excitation spectrum

Competition between excitation and electronic decay of short-lived molecular states

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