Direct Signature of Light-Induced Conical Intersections in Diatomics

Halász, Gábor J.; Vibók, Ágnes; Cederbaum, Lorenz S.

doi:10.1021/jz502468d

Cited by 92 publications

(105 citation statements)

References 71 publications

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“…This will change angular distributions by adding more adiabatic type dissociation events, decreasing the contrast of the interferences and adding to the distribution signal at smaller angles. Nevertheless, we note that similar quantum interferences in photodissociation of diatomic molecules were also theoretically discussed very recently in the framework of LICI [18,19] and our analysis is consistent with these studies.…”

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confidence: 92%

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Observation of Quantum Interferences via Light-Induced Conical Intersections in Diatomic Molecules

et al. 2016

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We observe energy-dependent angle-resolved diffraction patterns in protons from strong-field dissociation of the molecular hydrogen ion H + 2 . The interference is a characteristic of dissociation around a laser-induced conical intersection (LICI), which is a point of contact between two surfaces in the dressed 2-dimensional Born-Oppenheimer potential energy landscape of a diatomic molecule in a strong laser field. The interference magnitude and angular period depend strongly on the energy difference between the initial state and the LICI, consistent with coherent diffraction around a cone-shaped potential barrier whose width and thickness depend on the relative energy of the initial state and the cone apex. These findings are supported by numerical solutions of the time-dependent Schrödinger equation for similar experimental conditions.The Born-Oppenheimer approximation (BOA) represents intramolecular dynamics as the motion of nuclear wave packets on potential energy surfaces (PES) of electronic eigenvalues embedded in the space of nuclear geometries. A molecule on a single PES remains there so long as the adiabatic condition is obeyed, i.e. so long as nuclear kinetic energies are small compared to electronic state separations. This assumption must break down, however, if two or more PESs approach each other [1][2][3]. When this happens non-adiabatic couplings between the nearly-degenerate surfaces become important. The true eigenvalues can then be calculated by diagonalizing the Hamiltonian in the reduced space of the near degeneracy.According to simple geometrical arguments, molecules with at least two dimensions of internal nuclear motion (i.e. three or more atoms) must have some points where two or more PESs become degenerate, a condition known as a conical intersection (CI) [4]. These CIs play a key role in the relaxation dynamics of most polyatomic molecules including important biochemical processes such as the photostability of DNA [5], and the preliminary process of vision [6]. The dimension of the CI manifold is two less than the internal nuclear geometry. Thus for the simplest case of a tri-atomic molecule, the CI manifold has dimensionality of 3N − 8 = 1. The topological nature of CIs allows the nonadiabatic couplings to diverge and thus display related phenomena such as a geometric or Berry's phase [4,7] in wavepackets that circumnavigate the CI.Naturally occurring CIs cannot exist for a free diatomic molecule because the internuclear separation vector R is the only internal nuclear degree of freedom, and this is insufficient to fulfil the crossing condition. The nonadiabatic terms in the full Hamiltonian cause the BOA states to repel according to the so-called "no-crossing" rule. A diatomic molecule in a strong laser field, however, has a second degree of freedom defined by the laser polarization ε. When viewed in a Floquet basis of laserdressed electronic states, a molecule coupled by this field can exhibit a point of degeneracy called a light-induced conical intersection (LICI) in the 2−dimension...

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confidence: 92%

“…A signature of LICI's is quantum interference in strong-field laser-induced dissociation of the hydrogen or deuterium molecular ion [18,19]. Calculations predict that the interference produces modulations of the angular distributions of the dissociated fragments.…”

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confidence: 99%

Observation of Quantum Interferences via Light-Induced Conical Intersections in Diatomic Molecules

et al. 2016

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“…In the following we call these CIs, which originate from the field free electronic structure, natural CIs.Nonadiabatic effects can also appear when molecules are exposed to resonant laser light. The electric field can couple to two or more electronic states of the molecule via the non-vanishing transition dipole moment(s) [12][13][14][15]. This results either in a light-induced avoided crossing (LIAC) or a light-induced conical intersection (LICI) depending on how many nuclear degrees of freedom are involved in the field induced process [16].…”

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Ultrafast dynamics in the vicinity of quantum light-induced conical intersections

et al. 2019

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Nonadiabatic effects appear due to avoided crossings or conical intersections (CIs) that are either intrinsic properties in field-free space or induced by a classical laser field in a molecule. It was demonstrated that avoided crossings in diatomics can also be created in an optical cavity. Here, the quantized radiation field mixes the nuclear and electronic degrees of freedom creating hybrid fieldmatter states called polaritons. In the present theoretical study we go further and create CIs in diatomics by means of a radiation field in the framework of cavity quantum electrodynamics. By treating all degrees of freedom, that is the rotational, vibrational, electronic and photonic degrees of freedom on an equal footing we can control the nonadiabatic quantum light-induced dynamics by means of CIs. First, the pronounced difference between the the quantum light-induced avoided crossing and the CI with respect to the nonadiabatic dynamics of the molecule is demonstrated. Second, we discuss the similarities and differences between the classical and the quantum field description of the light for the studied scenario.The dynamics initiated in a molecule by absorbing a photon is often described in the Born-Oppenheimer (BO) or adiabatic approximation [1], where the electronic and nuclear degrees of freedom are treated separately. However, in some nuclear configurations called conical intersections (CIs) the mixing between the electronic and nuclear motions are very significant [2][3][4][5][6]. Owing to the strong nonadiabatic couplings (NACs) in the close vicinity of these CIs the BO approximation breaks down. It is well-known that these CIs have a significant impact on several important photo-dynamical processes, such as vision, photosynthesis, molecular electronics, and the photochemistry of DNA [7][8][9][10][11]. During the dynamics the CIs can serve as efficient decay channels for the ultrafast transfer of the populations. In the following we call these CIs, which originate from the field free electronic structure, natural CIs.Nonadiabatic effects can also appear when molecules are exposed to resonant laser light. The electric field can couple to two or more electronic states of the molecule via the non-vanishing transition dipole moment(s) [12][13][14][15]. This results either in a light-induced avoided crossing (LIAC) or a light-induced conical intersection (LICI) depending on how many nuclear degrees of freedom are involved in the field induced process [16]. In case of poly atomic molecules a sufficient number of vibrational degrees of freedom are always present to span a twodimensional branching space (BS), which is indispensable to the formation of LICI. In the case of diatomics one always has to find a proper second degree of freedom (DOF) which can act as a dynamical variable to form a BS. As the molecule rotates [17][18][19], the rotational angle between the molecular axis and the light polarization axis can serve as the missing DOF for establishing the BS [20].Nonadiabatic effects can arise in an optical or mi...

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“…The adiabatic potentials that incorporate these laser-molecule coupling effects are called light-induced potentials [28] (LIPs), while the avoided crossings in the LIPs are called light-induced avoided crossings [29,30] (LIACs). In polyatomic molecules, or taking into account the vectorial nature of the coupling, the LIACs can be seen as light-induced conical intersections [31][32][33][34][35][36][37][38][39] (LICIs). Considerable theoretical effort has been put recently at characterizing the LICIs.…”

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confidence: 99%

Molecular events in the light of strong fields: A light‐induced potential scenario

Chang

Solá

Shin

2016

Int J of Quantum Chemistry

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A new perspective on how to manipulate molecules by means of very strong laser pulses is emerging with insights from the so-called light-induced potentials, which are the adiabatic potential energy surfaces of molecules severely distorted by the effect of the strong field. Different effects appear depending on how the laser frequency is tuned, to a certain electronic transition, creating light-induced avoided crossings, or very off-resonant, generating Stark shifts. In the former case it is possible to induce dramatic changes in the geometry and redistribution of charges in the molecule while the lasers are acting and to fully control photodissociation reactions as well as other photochemical processes. Several theoretical proposals taken from the work of the authors are reviewed and analyzed showing the unique features that the strong-laser chemistry opens to control the transient properties and the dynamics of molecules.

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Direct Signature of Light-Induced Conical Intersections in Diatomics

Cited by 92 publications

References 71 publications

Observation of Quantum Interferences via Light-Induced Conical Intersections in Diatomic Molecules

Observation of Quantum Interferences via Light-Induced Conical Intersections in Diatomic Molecules

Ultrafast dynamics in the vicinity of quantum light-induced conical intersections

Molecular events in the light of strong fields: A light‐induced potential scenario

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