Femtochemistry

Sarkisov, O. M.; Umanskii, S. Ya.

doi:10.1070/rc2001v070n06abeh000664

Cited by 24 publications

(8 citation statements)

References 78 publications

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“…4) exhibit oscillations due to excitation of the coherent vibrational wave packet [9,10]. The oscillation issue is beyond the scope of this study.…”

Section: Sample Preparation Proceduresmentioning

confidence: 93%

Pulse heating of water at the surface of gold nanoparticles: Femtosecond laser spectroscopy of energy relaxation of aqueous colloid of plasmonic nanoparticles under strong excitation conditions

et al. 2015

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The plasmon peak of gold nanoparticles (AuNP) is due to resonance of plasma oscillations of conduction electrons of the metal. The frequency of the AuNP plasmon band peak is determined by the parameters at which Frohlich's resonance occurs [1]. For spherical Au nanoparticles, the Frohlich condition is achieved when + where = + is the dielectric permittivity of AuNP and ε d is the dielectric permittivity of the medium surrounding the AuNP. The AuNP plasmon resonance peak can be used as an optical sensor, since its position depends on the dielectric constant of the metal and the medium, which in turn depend on the temperature/pressure. Extinction, absorption, and scattering cross sections σ ext, abs, scat of the plasmon peak are usually expressed through nanoparticle geometric section πr 2 and factor Q ext, abs, scat : σ ext, abs, scat = Q ext, abs, scat πr 2 . Near the plas mon resonance peak, Q abs > 1, which means strong absorption of light by AuNP. At a high energy density of a femtosecond laser excitation pulse, temperature and pressure jumps in the AuNP and the adjacent nanolayer of surrounding water can be expected because of the strong absorption by AuNP [2]. There are several AuNP heating modes: (1) the AuNP lattice temperature Т does not exceed 100°C, the boiling(2) Т does not exceed the critical temperature of water of 373.95°C (pressure of 22.06 MPa), T vap < T < T cr ; (3) Т does not exceed the melting point of the metal 1063°C, T cr < T < T AuM ; and (4) Т does not exceed the boiling point of the metal T AuM < T < T AuB . The relaxation dynamics of the energy absorbed in the AuNP plasmon reso nance substantially affects the dynamics of heating and pressure rise in the surrounding layer of water. Under femtosecond pulse excitation, the light energy absorption/relaxation processes are considered in terms of the following model: absorption of a quantum of light and plasmon excitation → plasmon decay yielding hot (nonthermalized) electron → thermaliza tion of the electron and electron gas heating in the metal conduction band to a temperature T e → metal lattice heating to a temperature T L via electron-lattice relaxation → energy transfer to the environment [3]. Mathematically, the dynamics of these processes are modeled using the Anisimov two temperature model and numerical solution of the Navier-Stokes equa tions [4]. The problem is that the numerical solutions of these equations in the case of strong temperature and pressure gradients, first, are hampered by techni cal difficulties of computation and, second, ignore sig NANOSTRUCTURED SYSTEMS AND MATERIALSAbstract-The dynamics of differential absorption spectra of gold nanoparticles has been studied by femto second laser spectroscopy over a wide range of excitation energy density. The position of the plasmon reso nance peak strongly depends on the dielectric properties of the medium, thereby allowing the use of plas monic nanoparticles as an optical probe. It has been shown that femtosecond laser spectroscopy techniques, involving analysis of different...

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“…4) exhibit oscillations due to excitation of the coherent vibrational wave packet [9,10]. The oscillation issue is beyond the scope of this study.…”

Section: Sample Preparation Proceduresmentioning

confidence: 93%

Pulse heating of water at the surface of gold nanoparticles: Femtosecond laser spectroscopy of energy relaxation of aqueous colloid of plasmonic nanoparticles under strong excitation conditions

et al. 2015

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“…A sense of the history of this search, the contributions of others, and the very wide ranging applicability of the results can be gauged from Polanyi and Zewail's 1995 review [4]. In modern times, this field is often called either "transition-state spectroscopy", as it involves vibrational and electronic spectroscopies performed at geometries near the transition state, or else "femtochemistry", owing to the small time period during which such geometries are sustained and the spectra of interest generated [5][6][7][8][9][10][11][12][13]. Starting with the initial spectral analysis of Volker, Metiu, Almeida, Marcus, and Zewail [14], the conceptual basis of femtochemistry has been seeded in the time-dependent understanding of spectroscopy pioneered by Heller [15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Relating transition-state spectroscopy to standard chemical spectroscopic processes

Reimers

Hush

2017

Chemical Physics Letters

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Transition-state spectra are mapped out using generalized adiabatic electron-transfer theory. This simple model depicts diverse chemical properties, from aromaticity, through bound reactions such as isomerizations and atom-transfer processes with classic transition states, to processes often described as being "non-adiabatic", to those in the "inverted" region that become slower as they are made more exothermic. Predictably, the Born-Oppenheimer approximation is found inadequate for modelling transition-state spectra in the weak-coupling limit. In this limit, the adiabatic Born-Huang approximation is found to perform much better than non-adiabatic surfacehopping approaches. Transition-state spectroscopy is shown to involve significant quantum entanglement between electronic and nuclear motion. Highlights-transition-state spectra are calculated over a wide parameter region-spectral and temporal responses may be simple or quite complex-surface hopping methods fail to describe spectra usually classified as "non-adiabatic"-transition-state spectroscopy embodies quantum entanglement

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“…A new direction in chemical physics, femtochemistry, appeared. Many works were concerned with experi mental and theoretical femtochemical studies, in par ticular, with coherent dynamics control of various reactions (e.g., see reviews [1][2][3][4][5][6]). Modern interests in femtochemistry almost fully shifted toward studies of processes in condensed media (in the first place, in liquids) and coherent process control [3][4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Relaxation of excited molecules in a medium with memory at short and long times

Moskalenko

Umanskii

2012

Russ. J. Phys. Chem. B

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Two qualitatively different approaches to the dynamics of vibrational wave packets in the presence of medium induced relaxation, with taking into account relaxation memory effects and without taking them into account (Makovian approximation) were compared for a molecular system with one vibrational degree of freedom (the Morse oscillator) in a medium. The time evolution of the populations of levels, mean system energy, and response of "pumping-probing" experiments were calculated. It was found that, as distinct from the Markovian approximation, the approach including memory effects can predict the evolution of a molec ular system satisfying the detailed equilibrium principle. The two approaches specified also predict the exist ence of a qualitative difference of phase characteristics in the behavior of the system at short times.

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Femtochemistry

Cited by 24 publications

References 78 publications

Pulse heating of water at the surface of gold nanoparticles: Femtosecond laser spectroscopy of energy relaxation of aqueous colloid of plasmonic nanoparticles under strong excitation conditions

Pulse heating of water at the surface of gold nanoparticles: Femtosecond laser spectroscopy of energy relaxation of aqueous colloid of plasmonic nanoparticles under strong excitation conditions

Relating transition-state spectroscopy to standard chemical spectroscopic processes

Relaxation of excited molecules in a medium with memory at short and long times

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