Angular Dependence of Strong Field Ionization of 2-Phenylethyl-<i>N</i>,<i>N</i>-dimethylamine (PENNA) Using Time-Dependent Configuration Interaction with an Absorbing Potential

Hoerner, Paul; Li, Wen; Schlegel, H. Bernhard

doi:10.1021/acs.jpca.0c03438

Cited by 11 publications

(5 citation statements)

References 24 publications

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“…On the other hand, within the adiabatic approximation the initial-state dependence vanishes since the XC kernel is fully specified in terms of the instantaneous time-evolving density. 436 The topic of strong-field electron dynamics and how it can be described using TDKS calculations is not considered here, except to note that there have been successful TDKS simulations of strong-field photoionization, [437][438][439][440][441][442][443][444][445][446][447][448] and also of high harmonic generation, [449][450][451][452][453][454][455][456][457] both in Gaussian-orbital representations of the density. Unlike the gridbased treatments that are common in atomic physics, Gaussian-based methods are scalable to molecules.…”

Section: Theorymentioning

confidence: 99%

Density Functional Theory for Electronic Excited States

Herbert¹

2022

Preprint

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This chapter provides a basic introduction to excited-state extensions of density functional theory (DFT), including time-dependent (TD-)DFT in both its linear-response and its explicitly time-dependent formulations. As applied to the Kohn-Sham DFT ground state, linear-response theory affords an eigenvaluetype problem for the excitation energies in a basis of singly-excited Slater determinants, and is widely known simply as "TDDFT" despite its frequency-domain formulation. This form of TDDFT is the mostly widely-used quantum-chemical method for excited states, due to a favorable combination of low cost and reasonable accuracy. The chapter surveys the accuracy of linear-response TDDFT, which is generally more sensitive to the details of the exchange-correlation functional as compared to ground-state DFT, and also describes some known systemic problems exhibited by this approach. Some of those problems can be corrected on a case-by-case basis using orbital-optimized, excited-state self-consistent field (SCF) calculations, in what is known as excited-state Kohn-Sham theory or a "∆SCF" procedure, a class of methods that includes restricted open-shell Kohn-Sham theory. Recent successes of these approaches are highlighted, including double excitations and core-level excitations. Finally, explicitly time-dependent (or "real-time") TDDFT involves propagation of the molecular orbitals in time following an external perturbation, according to the Kohn-Sham analogue of the time-dependent Schrödinger equation. The time-dependent approach has been used to model strong-field electron dynamics, and in the weak-field limit it provides a route to broadband spectra based on the time evolution of the dipole moment function. This is useful for describing high-energy excitations (as in x-ray spectroscopy) and in systems where the density of states is high, as demonstrated by a few examples.

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Section: Theorymentioning

confidence: 99%

Density Functional Theory for Electronic Excited States

Herbert¹

2022

Preprint

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“…HCCF ionizes primarily from the CC π-bond with no contribution from F, while HCCI ionizes mainly from I with a small component from the CC π-bond. Strong field ionization of 2-phenylethyl- N , N -dimethylamine (PENNA) is the largest system that we have studied to date with TD-CIS …”

Section: Applications Of Direct Dynamicsmentioning

confidence: 99%

“…Strong field ionization of 2-phenylethyl-N,N-dimethylamine (PENNA) is the largest system that we have studied to date with TD-CIS. 87 Intense laser pulses can cause multiple ionizations. Sequential double ionization can dominate for over-the-barrier ionization.…”

Section: Strong Field Electron Dynamicsmentioning

confidence: 99%

Ab Initio Direct Dynamics

Schlegel

2021

Acc. Chem. Res.

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Conspectus The reactivity and dynamics of molecular systems can be explored computationally by classical trajectory calculations. The traditional approach involves fitting a functional form of a potential energy surface (PES) to the energies from a large number of electronic structure calculations and then integrating numerous trajectories on this fitted PES to model the molecular dynamics. The ever-decreasing cost of computing and continuing advances in computational chemistry software have made it possible to use electronic structure calculations directly in molecular dynamics simulations without first having to construct a fitted PES. In this “on-the-fly” approach, every time the energy and its derivatives are needed for the integration of the equations of motion, they are obtained directly from quantum chemical calculations. This approach started to become practical in the mid-1990s as a result of increased availability of inexpensive computer resources and improved computational chemistry software. The application of direct dynamics calculations has grown rapidly over the last 25 years and would require a lengthy review article. The present Account is limited to some of our contributions to methods development and various applications. To improve the efficiency of direct dynamics calculations, we developed a Hessian-based predictor-corrector algorithm for integrating classical trajectories. Hessian updating made this even more efficient. This approach was also used to improve algorithms for following the steepest descent reaction paths. For larger molecular systems, we developed an extended Lagrangian approach in which the electronic structure is propagated along with the molecular structure. Strong field chemistry is a rapidly growing area, and to improve the accuracy of molecular dynamics in intense laser fields, we included the time-varying electric field in a novel predictor-corrector trajectory integration algorithm. Since intense laser fields can excite and ionize molecules, we extended our studies to include electron dynamics. Specifically, we developed code for time-dependent configuration interaction electron dynamics to simulate strong field ionization by intense laser pulses. Our initial application of ab initio direct dynamics in 1994 was to CH2O → H2 + CO; the calculated vibrational distributions in the products were in very good agreement with experiment. In the intervening years, we have used direct dynamics to explore energy partitioning in various dissociation reactions, unimolecular dissociations yielding three fragments, reactions with branching after the transition state, nonstatistical dynamics of chemically activated molecules, dynamics of molecular fragmentation by intense infrared laser pulses, selective activation of specific dissociation channels by aligned intense infrared laser fields, angular dependence of strong field ionization, and simulation of sequential double ionization.

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“…Beyond the 3SM, to capture qualitatively and quantitatively fine features of HHG spectra and complexity of the field-induced dynamics requires a first-principle approach. Indeed, real-time time-dependent electronic-structure wavefunction-based methods (RT-TD-WF) have been successfully applied to strong-field electronic dynamics. ,,− Time propagation can be carried out in the space of molecular orbitals (MOs) ,− , or in the space of the field-free eigenstates of the atom or molecule. ,,,,− …”

Section: Introductionmentioning

confidence: 99%