Program for quantum wave-packet dynamics with time-dependent potentials

Dion, Claude M.; Hashemloo, Ali; Rahali, G.

doi:10.1016/j.cpc.2013.09.012

Cited by 21 publications

(17 citation statements)

References 19 publications

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“…The TDSE has been solved by using a modified ver- sion of the split-operator technique [74]. We have used a spatial grid of equidistant points with ∆z = 0.1 a.u.…”

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confidence: 99%

Tuning high-harmonic generation by controlled deposition of ultrathin ionic layers on metal surfaces

Aguirre

Martín

2016

Phys. Rev. B

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High harmonic generation (HHG) from semiconductors and insulators has become a very active area of research due to its great potential for developing compact HHG devices. Here we show that by growing monolayers (ML) of insulators on single-crystal metal surfaces, one can tune the harmonic spectrum by just varying the thickness of the ultrathin layer, not the laser properties. This is shown from numerical solutions of the time-dependent Schrödinger equation for nML NaCl/Cu(111) systems (n = 1 − 50) based on realistic potentials available in the literature. Remarkably, the harmonic cutoff increases linearly with n and as much as an order of magnitude when going from n = 1 to 30, while keeping the laser intensity low and the wavelength in the near-infrared range. Furthermore, the degree of control that can be achieved in this way is much higher than by varying the laser intensity. The origin of this behavior is the reduction of electronic "friction" when moving from the essentially discrete energy spectrum associated with a few-ML system to the continuous energy spectrum (bands) inherent to an extended periodic system. PACS numbers: 42.65. Ky,78.66.Nk, Discovered in the 1980's [1-3], high harmonic generation (HHG) has become the fundamental tool of modern attoscience [4][5][6]. In HHG from atomic or molecular gases, a strong laser field ionizes an electron, which then gains energy from the field and returns to the parent ion, where it finally recombines converting the gained energy into high-frequency radiation [7][8][9][10]. The process repeats every half-cycle of the ionizing field, thus leading to a sequence of attosecond light bursts that contain multiples of the fundamental laser frequency, ω 0 . Since electronic motion in atomic and molecular systems occurs in the attosecond time scale, light pulses arising from HHG are currently used to probe electron dynamics in those systems [11][12][13][14][15][16][17][18]. Furthermore the HHG process itself contains the signature of the parent-ion dynamics occurring during the round trip of the traveling electron. Thus the analysis of the HHG spectral features can also reveal important aspects of such dynamics [19][20][21][22][23][24][25].HHG from condensed matter systems was first observed in the mid 90s [26,27]. In these early experiments, bulk metals and dielectrics irradiated with very intense near-infrared laser fields (of the order of 10 18 W/cm 2 ) were shown to emit harmonic radiation as a result of plasma oscillations induced in the system (see also [28]) Due to the high intensity of the field, HHG was always accompanied by sample damage. More recent experiments have made use of nano tips and nano spheres [29][30][31][32][33], from which HHG has been produced by using relatively moderate fields (of the order of 10 12 W/cm 2 ). HHG has also been observed in bulk semiconductors and insulators [34][35][36][37][38][39][40] by using similar low intensities (even lower than those usually needed to generate high harmonics in the gas phase) and longer wavelengths, down ...

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“…The TDSE has been solved by using a modified ver- sion of the split-operator technique [74]. We have used a spatial grid of equidistant points with ∆z = 0.1 a.u.…”

mentioning

confidence: 99%

Tuning high-harmonic generation by controlled deposition of ultrathin ionic layers on metal surfaces

Aguirre

Martín

2016

Phys. Rev. B

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“…The selected optimal target states have provided a feasible route of photoassociation for alkaline earth dimers. The quantitative yield and purity of the target state after photoassociation have been studied by using quantum wavepacket dynamic methods . Combining with highly correlated ab initio calculations for accurate determination of the PECs and TDMCs, one could calculate the photon energy absorption cross sections of photoassociation.…”

Section: Theories and Methodsmentioning

confidence: 99%

“…According to Fourier grid Hamiltonian method for the state eigenvalues and eigenfunctions, we precomputed the main vibrational eigenstates Ψ' ν ( R , t ) of the potential using the program . The projections of the wavepacket Φ( R , t ) on the vibrational eigenstates Ψ' ν ( R , t ) of the excited state are calculated by using the same grid, which are used to represent the yields of photoassociations.

ρ_{v} ((), t) = {|(〈〉|, ψ'_{ν} ((), R, t), normalΦ ((), R, t))|}^{2},

where Ψ” ν ( R , t ) represents the eigenfunction of the ground state and Ψ' ν ( R , t ) represents the eigenfunction of the excited state.…”

Section: Theories and Methodsmentioning

confidence: 99%

Selective control of photoassociation of alkaline earth dimers: A theoretical study

Cheng

Zhang

Cheng

et al. 2019

Int J of Quantum Chemistry

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The laser synthesis of alkaline earth dimers (Be2, Mg2, Ca2, Sr2, and Ba2) is investigated by theoretical calculation. Photoassociation based on ab initio calculations is rationalized by Franck‐Condon filtering. The optimal target states of photoassociations have been obtained, which are A1∑+u state for Be2, Mg2, and Ca2, and are B1∑+u state for Sr2 and Ba2, corresponding to vibrational transition bands from X1∑+g to excited state are 0‐1, 0‐7, 0‐10, 0‐13, and 0‐3, respectively. The proposed laser drive transitions to target states are also investigated that range from 350 to 740 nm. By using quantum wave‐packet dynamic methods, we calculated the absorption cross sections of photon energy and yields for the selected states of photoassociation. It show that the most sensitive molecules for quantum selective control of photoassociation are Be2 and Ba2 for alkaline earth dimers. These important parameters will provide a feasible scheme for further experimental researches.

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“…The time-dependent Schrödinger equation for a specific initial quantum state is solved numerically using the split operator technique [ 42 , 43 ]. As this is a well-known technique, we provide a brief description of the method.…”

Section: Quantum Wavepacket Dynamicsmentioning

confidence: 99%

Classical and Quantum Dynamical Manifestations of Index-$$2$$ Saddles: Concerted Versus Sequential Reaction Mechanisms

2021

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The presence of higher-index saddles on a multidimensional potential energy surface is usually assumed to be of little significance in chemical reaction dynamics. Such a viewpoint requires careful reconsideration, thanks to elegant experiments and novel theoretical approaches that have come about in recent years. In this work, we perform a detailed classical and quantum dynamical study of a model two-degree-of-freedom Hamiltonian, which captures the essence of the debate regarding the dominance of a concerted or a stepwise reaction mechanism. We show that the ultrafast shift of the mechanism from a concerted to a stepwise one is essentially a classical dynamical effect. In addition, due to the classical phase space being a mixture of regular and chaotic dynamics, it is possible to have a rich variety of dynamical behavior, including a Murrell – Laidler type mechanism, even at energies sufficiently above that of the index- saddle. We rationalize the dynamical results using an explicit construction of the classical invariant manifolds in the phase space. Supplementary Information The online version contains supplementary material with details on computation of the invariant manifolds which available at 10.1134/S1560354721020052.

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Program for quantum wave-packet dynamics with time-dependent potentials

Cited by 21 publications

References 19 publications

Tuning high-harmonic generation by controlled deposition of ultrathin ionic layers on metal surfaces

Tuning high-harmonic generation by controlled deposition of ultrathin ionic layers on metal surfaces

Selective control of photoassociation of alkaline earth dimers: A theoretical study

Classical and Quantum Dynamical Manifestations of Index-$$2$$ Saddles: Concerted Versus Sequential Reaction Mechanisms

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