Search

The use of cavities to impact molecular structure and dynamics has become popular. As cavities, in particular plasmonic nanocavities, are lossy and the lifetime of their modes can be very short, their lossy nature must be incorporated into the calculations. The Lindblad master equation is commonly considered an appropriate tool to describe this lossy nature. This approach requires the dynamics of the density operator and is thus substantially more costly than approaches employing the Schrödinger equation for the quantum wave function when several or many nuclear degrees of freedom are involved. In this work, we compare numerically the Lindblad and Schrödinger descriptions discussed in the literature for a molecular example where the cavity is pumped by a laser. The laser and cavity properties are varied over a range of parameters. It is found that the Schrödinger description adequately describes the dynamics of the polaritons and emission signal as long as the laser intensity is moderate and the pump time is not much longer than the lifetime of the cavity mode. Otherwise, it is demonstrated that the Schrödinger description gradually fails. We also show that the failure of the Schrödinger description can often be remedied by renormalizing the wave function at every step of time propagation. The results are discussed and analyzed. [ABSTRACT FROM AUTHOR]

The exchange of energy between electronic and nuclear motion is the origin of non-adiabaticity and plays an important role in many molecular phenomena and processes. Conical intersections (CIs) of different electronic potential energy surfaces lead to the most singular non-adiabaticity and have been intensely investigated. The coupling of light and matter induces conical intersections, which are termed light-induced conical intersections (LICIs). There are two kinds of LICIs, those induced by classical (laser) light and those by quantum light like that provided by a cavity. The present work reviews the subject of LICIs, discussing the achievements made so far. Particular attention is paid to comparing classical and quantum LICIs, their similarities and differences and their relationship to naturally occurring CIs. In contrast to natural CIs, the properties of which are dictated by nature, the properties of their light-induced counterparts are controllable by choosing the frequency and intensity (or coupling to the cavity) of the external light source. This opens the door to inducing and manipulating various kinds of non-adiabatic effects. Several examples of diatomic and polyatomic molecules are presented covering both dynamics and spectroscopy. The computational methods employed are discussed as well. To our opinion, the young field of LICIs and their impact shows much future potential. [ABSTRACT FROM AUTHOR]

It has been known that electronic conical intersections in a molecular system can also be created by laser light even in diatomics. The direct consequence of these light-induced degeneracies is the appearance of a strong mixing between the electronic and vibrational motions, which has a strong fingerprint on the ultrafast nuclear dynamics. In the present work, pump and probe numerical simulations are performed with the NaH molecule involving the first three singlet electronic states (X1Σ+(X), A1Σ+(A) and B1Π(B)) and several light-induced degeneracies in the numerical description. To demonstrate the impact of the multiple light-induced non-adiabatic effects together with the molecular rotation on the dynamical properties of the molecule, the dissociation probabilities, kinetic energy release spectra (KER) and the angular distributions of the photofragments were calculated by discussing the role of the permanent dipole moment as well. [ABSTRACT FROM AUTHOR]

Nonadiabatic coupling is absent between the electronic ground X and first excited (singlet) A states of formaldehyde. As laser fields can induce conical intersections between these two electronic states, formaldehyde is particularly suitable for investigating light-induced nonadiabaticity in a polyatomic molecule. The present work reports on the spectrum induced by light—the so-called field-dressed spectrum—probed by a weak laser pulse. A full-dimensional ab initio approach in the framework of Floquet-state representation is applied. The low-energy spectrum, which without the dressing field would correspond to an infrared vibrational spectrum in the X-state, and the high-energy spectrum, which without the dressing field would correspond to the X → A spectrum, are computed and analyzed. The spectra are shown to be highly sensitive to the frequency of the dressing light allowing one to isolate different nonadiabatic phenomena. [ABSTRACT FROM AUTHOR]

Nonadiabatic phenomena are investigated in the rovibrational motion of molecules confined in an infrared cavity. Conical intersections (CIs) between vibrational polaritons, similar to CIs between electronic polaritonic surfaces, are found. The spectral, topological, and dynamic properties of the vibrational polaritons show clear fingerprints of nonadiabatic couplings between molecular vibration, rotation, and the cavity photonic mode. Furthermore, it is found that for the investigated system, composed of two rovibrating HCl molecules and the cavity mode, breaking the molecular permutational symmetry, by changing 35 Cl to 37 Cl in one of the HCl molecules, the polaritonic surfaces, nonadiabatic couplings, and related spectral, topological, and dynamic properties can deviate substantially. This implies that the natural occurrence of different molecular isotopologues needs to be considered when modeling realistic polaritonic systems. [ABSTRACT FROM AUTHOR]

The coupling of a molecule to a cavity can induce conical intersections of the arising polaritonic potential energy surfaces. Such intersections give rise to the strongest possible nonadiabatic effects. By choosing an example that does not possess nonadiabatic effects in the absence of the cavity, we can study, for the first time, the emergence of these effects in a polyatomic molecule due to its coupling with the cavity taking into account all vibrational degrees of freedom. The results are compared with those of reduced-dimensionality models, and the shortcomings and merits of the latter are analyzed. [ABSTRACT FROM AUTHOR]

The formation of light-induced conical intersections (LICIs) between electronic states of diatomic molecules has been thoroughly investigated over the past decade. In the case of running laser waves, the rotational, vibrational, and electronic motions couple via the LICI giving rise to strong nonadiabatic phenomena. In contrast to natural conical intersections (CIs) which are given by nature and hard to manipulate, the characteristics of LICIs are easily modified by the parameters of the laser field. The internuclear position of the created LICI is determined by the laser energy, while the angular position is given by the orientation of the transition dipole moment (TDM) with respect to the molecular axis. In the present communication, using MgH+ as a showcase example, we exploit the strong impact of the orientation of the TDMs exerted on the light-induced nonadiabatic dynamics. Comparing the photodissociations induced by parallel or perpendicular transitions, a clear signature of the created LICIs is revealed in the angular distribution of the photofragments. [ABSTRACT FROM AUTHOR]

Polaritons – hybrid light-matter states formed in cavity – strongly change the properties of the underlying matter. In optical or plasmonic nanocavities, polaritons decay by radiative emission of the cavity, which is accessible experimentally. Due to the interaction of a molecule with the quantized radiation field, polaritons exhibit light-induced conical intersections (LICIs) which dramatically influence the nuclear dynamics of molecular polaritons. We show that ultrafast radiative emission from the lower polariton is controlled by the geometric phase imposed by the LICI. This finding provides insight into the process of emission and, furthermore, allows one to compute these signals by augmenting the Born–Oppenheimer approximation for polaritons with a geometric phase term. [ABSTRACT FROM AUTHOR]

Conical intersections are degeneracies between multidimensional potential energy surfaces of molecular systems. It is well known that, besides these phenomena significantly modify the spectroscopic and dynamical properties of molecules, their presence in a molecular system has noticeable topological implications, as well. Such a consequence is the appearance of the topological or geometric phase. Conical intersections not only occur in nature but they can also be created by light. This can either be classical laser light or quantum light in an optical cavity. As a showcase example, by placing the formaldehyde (H2CO) molecule into a cavity, the topological properties (e.g., geometric or Berry phase) of the emerging light‐induced conical intersection have been investigated for different cavity parameters and geometrical arrangements. [ABSTRACT FROM AUTHOR]

Recently, the rovibronic absorption and emission spectra of diatomic molecules dressed by medium‐intensity laser fields have been discussed. By computing the total absorption probability as a function of dressing wavelength an asymmetric line shape has been obtained strongly resembling to the well‐known Fano line shape. Applying two‐state analytical and three‐state numerical models the shape of the total absorption probability function is explained. Further confirmation of the model based results is provided by high resolution accurate numerical computations using large number of basis functions. [ABSTRACT FROM AUTHOR]

In the presence of linearly varying frequency chirped laser pulses, the photodissociation dynamics of D2+ is studied theoretically after ionization of D2. As a completion of our recent work [A. Csehi et al., J. Chem. Phys. 143, 014305 (2015)], a comprehensive dependence on the pulse duration and delay time is presented in terms of total dissociation probabilities. Our numerical analysis carried out in the recently introduced light-induced conical intersection (LICI) framework clearly shows the effects of the changing position of the LICI which is induced by the frequency modulation of the chirped laser pulses. This impact is presented for positively, negatively, and zero chirped short pulses. [ABSTRACT FROM AUTHOR]

Recently, it has been revealed that so-called light-induced conical intersections (LICIs) can be formed both by standing or by running laser waves even in diatomic molecules. Due to the strong nonadiabatic couplings, the existence of such LICIs has significant impact on the dynamical properties of a molecular system. In our former studies, the photodissociation process of the D+2 molecule was studied initiating the nuclear dynamics both from individual vibrational levels and from the superposition of all the vibrational states produced by ionizing D2. In the present work, linearly chirped laser pulses were used for initiating the dissociation dynamics of D2+ . In contrast to the constant frequency (transform limited) laser fields, the chirped pulses give rise to LICIs with a varying position according to the temporal frequency change. To demonstrate the impact of these LICIs on the dynamical properties of diatomics, the kinetic energy release spectra, the total dissociation probabilities, and the angular distributions of the D2+ photofragments were calculated and discussed. [ABSTRACT FROM AUTHOR]

We present a theoretical approach for simulating rovibronic spectra of molecules dressed by medium-intensity laser fields. Numerical results, obtained through the formalism described, are presented for the homonuclear diatomic moleculeNa2, a system suitable for demonstrating and understanding various aspects of light-dressed spectroscopy. We discuss the physical origin of the peaks in the lightdressed spectrum of Na2 and investigate the light-dressed spectrum in terms of its dependence on the dressing field's intensity and wavelength, temperature, and the turn-on time of the dressing field. The possibility of using light-dressed spectroscopy to derive field-free spectroscopic quantities is also addressed. [ABSTRACT FROM AUTHOR]

We present various types of reduced models including five vibrational modes and three electronic states for the pyrazine molecule in order to investigate the lifetime of electronic coherence in a rigid and neutral system. Using ultrafast optical pumping in the ground state (11Ag), we prepare a coherent superposition of two bright excited states, 11B2u and 11B1u, and reveal the effect of the nuclear motion on the preservation of the electronic coherence induced by the laser pulse. More specifically, two aspects are considered: the anharmonicity of the potential energy surfaces and the dependence of the transition dipole moments (TDMs) with respect to the nuclear coordinates. To this end, we define an 'ideal model' by making three approximations: (i) only the five totally symmetric modes move, (ii) which correspond to uncoupled harmonic oscillators, and (iii) the TDMs from the ground electronic state to the two bright states are constant (Franck–Condon approximation). We then lift the second and third approximations by considering, first, the effect of anharmonicity, second, the effect of coordinate-dependence of the TDMs (first-order Herzberg–Teller contribution), third, both. Our detailed numerical study with quantum dynamics is meant to be realistic for pyrazine over about 20 femtoseconds, and was further extended so as to probe the effect of such approximations on a model system. We show that long-term revivals of the electronic coherence persist up to the picosecond time range even for the most realistic model. [ABSTRACT FROM AUTHOR]

A quantum system composed of a molecule and an atomic ensemble, confined in a microscopic cavity, is investigated theoretically. The indirect coupling between atoms and the molecule, realized by their interaction with the cavity radiation mode, leads to a coherent mixing of atomic and molecular states, and at strong enough cavity field strengths hybrid atom–molecule–photon polaritons are formed. It is shown for the Na2 molecule that by changing the cavity wavelength and the atomic transition frequency, the potential energy landscape of the polaritonic states and the corresponding spectrum could be changed significantly. Moreover, an unforeseen intensity borrowing effect, which can be seen as a strong nonadiabatic fingerprint, is identified in the atomic transition peak, originating from the contamination of the atomic excited state with excited molecular rovibronic states. [ABSTRACT FROM AUTHOR]

The absorption spectra of the cold Na2 molecule dressed by a linearly polarized standing laser wave is investigated with a theoretical model incorporating translational, electronic, vibrational as well as rotational degrees of freedom. In such a situation a light-induced conical intersection (LICI) can be formed (J. Phys. B: At. Mol. Opt. Phys., 2008, 41, 221001). To measure the spectra a weak field is used whose propagation direction is perpendicular to the direction of the dressing field but has identical polarization direction. Although LICIs are present in our model, the simulations demonstrate a very robust absorption spectrum, which is insensitive to the intensity and the wavelength of the dressing field and which does not reflect clear signatures of light-induced nonadiabatic phenomena related to the strong mixing between the electronic, vibrational, rotational and translational motions. However, by widening artificially the very narrow translational energy level gaps, the fingerprint of the LICI appears to some extent in the spectrum. [ABSTRACT FROM AUTHOR]

This paper is devoted to a specific difficulty related to the electronic nonadiabatic coupling terms (NACT), namely, how to determine correctly their signs. It is well known that correct NACTs, including their signs, are crucial for any numerical treatment of the nuclear Schrödinger equation [see, i.e., A. Kuppermaan and R. Abrol, Adv. Chem. Phys. 124, 283 (2003)]. In most cases the derivation of the correct sign of the nonadiabatic coupling matrix (NACM) is done employing various continuity procedures. However, there are cases where these procedures do not suffice and for these cases we suggest to apply an additional procedure based on a mathematical lemma which asserts that the exponentiated line integral which yields the D matrix is invariant with respect to the initial point of the integration [M. Baer, J. Phys. Chem. A 104, 3181 (2000)]. In the numerical study we apply this lemma to determine the signs of the 3×3 NACM elements for the three excited states of the {H2,O} system (some of these NACTs are presented here for the first time). It turns out that the ab initio treatment yields results from which one can form eight different 3×3 NACMs. However the application of this lemma (which does not require any significant additional numerical effort) reduces this number to two. The final selection is done by an enhanced numerical study which requires more accurate calculations. [ABSTRACT FROM AUTHOR]

Conical intersections are degeneracies between electronic states and are very common in nature. It has been found that they can also be created both by standing or by running laser waves. The latter are called light-induced conical intersections. It is well known that conical intersections are the sources for numerous topological effects which are manifested, e.g. in the appearance of the geometric or Berry phase. In one of our former works by incorporating the diabatic-to-adiabatic transformation angle with the line-integral technique, we have calculated the Berry-phase of the light-induced conical intersections. Here, we demonstrate that by using the time-dependent adiabatic approach suggested by Berry the geometric phase of the light-induced conical intersections can also be obtained and the results are very similar to those of the time-independent calculations. [ABSTRACT FROM AUTHOR]

Nonadiabatic effects play a very important role in controlling chemical dynamical processes. They are strongly related to avoided crossings (AC) or conical intersections (CIs) which can either be present naturally or induced by classical laser light in a molecular system. The latter are named as “light-induced avoided crossings” (LIACs) and “light-induced conical intersections” (LICIs). By performing one or two dimensional quantum dynamical calculations LIAC and LICI situations can easily be created even in diatomic molecules. Applying such calculations for the NaI molecule, which is a strongly coupled diatomic in field free case, significant differences between the impact of the LIAC and LICI on the ground state population dynamics were observed. Moreover, obtained results undoubtedly demonstrate that the effect of the LIAC and LICI on the dynamics strongly depends on the intensity and the frequency of the applied laser field as well as the permanent dipole moments of the molecule. [ABSTRACT FROM AUTHOR]

Light-induced conical intersections (LICIs) can be formed both by standing or by running laser waves. The position of a LICI is determined by the laser frequency while the laser intensity controls the strength of the nonadiabatic coupling. Recently, it was shown within the LICI framework that linearly chirped laser pulses have an impact on the dissociation dynamics of the D2+ molecule (J. Chem. Phys., 143, 014305, (2015); J. Chem. Phys., 144, 074309, (2016)). In this work we exploit this finding and perform calculations using chirped laser pulses in which the time dependence of the laser frequency is designed so as to force the LICI to move together with the field-free vibrational wave packet as much as possible. Since nonadiabaticity is strongest in the vicinity of the conical intersection, this is the first step towards controlling the dissociation process via the LICI. Our showcase example is again the D2+ molecular ion. To demonstrate the impact of the LICIs on the dynamical properties of diatomics, the total dissociation probabilities and the population of the different vibrational levels after the dissociation process are studied and discussed. [ABSTRACT FROM AUTHOR]

Nonadiabatic effects are ubiquitous in physics and chemistry. They are associated with conical intersections (CIs) which are degeneracies between electronic states of polyatomic molecules. Recently, it has been recognized that so-called light-induced conical intersections (LICIs) can be formed both by standing or by running laser waves even in diatomics. Owing to the strong nonadiabatic couplings, the appearance of such laser-induced conical intersections (LICIs) may significantly change the dynamical properties of a molecular system. In the present paper we investigate the photodissociation dynamics of D 2 + ion initiating the nuclear dynamics from the superposition of all the vibrational states produced by ionizing D 2 . The kinetic energy release and the angular distribution of the photodissociation products are computed with and without LICI for the several different values of the laser parameters. We performed both one- and two-dimensional calculations, as well. In the first scheme the molecules were rotationally frozen, whereas in the latter one, the molecular rotation is included as a full additional dynamic variable. The results obtained undoubtedly demonstrate that the impact of the LICI on the dissociation dynamics of the D 2 + molecule strongly depend upon the laser parameters applied. [ABSTRACT FROM AUTHOR]

The present study is concerned with the theoretical study of possible molecular switch systems. The 7-hydroxyquinoline-8-carboxamide molecule and its single-, double-, and triple-substituted derivatives are investigated with the aim of revealing characteristic switch features. Molecular switches can be considered as composed of a frame and a crane component. According to a recent study, the 7-hydroxyquinoline double-ring system constitutes the frame moiety, while a carboxamide group at position 8 plays the role of the crane part (Csehi et al., Phys. Chem. Chem. Phys. 2013, 15, 18048). The effect of single 2-,4-,6-methyl, double 2,4-, 2,6-diamino, and triple 2,4,6-triamino substitutions to the molecular frame has been investigated using high level ab initio techniques. As a possible reaction mechanism, excited state intramolecular hydrogen transfer mediated by the frame-crane torsion has been considered. At the terminal structures of this pathway, second-order approximate coupled-cluster (CC2) quality vertical excitation energies and oscillator strengths have been calculated for the three lowest-lying singlet electronic excited states of all the studied systems. Single point calculations at selected geometries of the reaction path were carried out at the CC2 level as well, while conical intersections (CIs) between the ground and first excited states near perpendicular twisted geometries were optimized using the complete active space self-consistent field method. To confirm the presence of CIs, nonadiabatic coupling terms have been derived and applying the topological line integral technique, the topological (or Berry) phase has been calculated surrounding the point of CI. The results of this work clearly demonstrate the fulfillment of several molecular switch properties by the investigated quinoline derivatives. An extensive comparison between the different compounds is presented as well. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The ground and five lowest-lying electronically excited singlet states of 2-(4-nitropyrimidin-2-yl)ethenol (NPE) have been studied theoretically using the complete active space self-consistent-field (CASSCF), Møller-Plesset second-order perturbation theory (MP2) and second-order multi-configurational perturbation theory (CASPT2) methods. The molecule can be regarded as being composed of a frame and a crane component and is characterised by the existence of two planar minima of similar energy on the ground-state potential energy (PE) surface. This work explores the possibility of an excited-state intramolecular hydrogen transfer (ESIHT) process in NPE. A hypothetical reaction coordinate has been constructed for NPE. State-averaged CASSCF and CASPT2 calculations of the six lowest-lying singlet states have been performed for the isomerisation. Adiabatic and simplified quasi-diabatic PE and transition dipole moment functions have been constructed. The computations indicate that there exist substantial barriers for the rotation process on the adiabatic PE surfaces of all the five excited states investigated. The six quasi-diabatic electronic states considered here decompose into two classes based on whether the electronic wave functions depend weakly or strongly on the nuclear displacement, subject to the effect of the torsion on relevant molecular orbitals. [ABSTRACT FROM AUTHOR]

This study investigates the effect of chemical substituents on the functional properties of a molecular photoswitch (Phys. Chem. Chem. Phys., 2008, 10, 1243) by means of theoretical tools. Molecular switches are known to consist of so-called frame and crane components. Several functional groups are substituted to the 7-hydroxyquinoline molecular frame at position 8 as crane fragments. The impact of π-electron donating NH2 groups attached to the frame is also investigated. Excited state intramolecular hydrogen transfer mediated by the frame-crane torsion has been considered as a possible reaction mechanism. For all the investigated systems, we present the resulting potential energy profiles of the ground and first excited states. Vertical excitation energies and oscillator strengths of the 5 lowest-lying excited electronic states calculated at the two terminal points of the reaction path are also presented. Single point calculations were carried out at the CC2 level, while the presence of conical intersections between the ground and first excited states near perpendicular twisted geometries was demonstrated using the CASSCF method. Our results undoubtedly reveal the fulfillment of several molecular switch properties of the studied quinoline compounds. Comparisons between the different substituted systems have also been made. [ABSTRACT FROM AUTHOR]

The six lowest lying electronic singlet states of 8-(pyrimidine-2-yl)quinolin-ol and 2-(4-nitropyrimidine-2-yl)ethenol have been studied theoretically using the complete active space self-consistent-field (CASSCF) and M’ller-Plesset second-order perturbation theory (MP2) methods. Both molecules can be viewed as consisting of a frame and a crane component. As a possible mechanism for the excited-state relaxation process an intramolecular hydrogen transfer promoted by twisting around the covalent bond connecting the molecular frame and crane moieties has been considered. Based on this idea we have attempted to derive abstracted photochemical pathways for both systems. Geometry optimizations for the construction of hypothetical reaction coordinates have been performed at the MP2 level of theory while the CASSCF approach has been employed for the calculation of vertical excitation energies along the pathways. The results of the calculations along the specific twisting displacements investigated in this study do not support the notion of substantial twisting activity upon excitation of any of the five excited states at the planar terminal structures of the torsion coordinates of both molecules. However, the present analysis should be considered only as a first, preliminary step towards an understanding of the photochemistry of the two candidate compounds. For example, we have not performed any excited state geometry optimizations so far and the estimates of vertical excitation energies do not take dynamical electron correlation into account. Further work on this subject is in progress. [ABSTRACT FROM AUTHOR]

An analysis of the charge transfer mechanism in the collision of multiply charged ions with molecular and biomolecular targets is performed, considering the non-adiabatic interactions between the molecular states involved. Collisions of doubly charged C2+ ions on small molecular targets, CO and OH, have been investigated, together with the analysis of charge transfer between C4+ ions on uracil and halouracil biomolecular targets. The process is studied theoretically by means of ab-initio molecular calculations followed by a semi-classical treatment of the collision dynamics. The influence of rotational couplings is discussed with regard to the collision energy. Strong anisotropic and vibration effects are pointed out. [ABSTRACT FROM AUTHOR]

It has recently been shown that dressing of diatomic molecules by standing or by running laser waves can give rise to the appearance of the so-called light-induced conical intersections (LICIs). The effect of these LICIs on different physical properties of the diatomic molecules has been demonstrated in several publications [1-6]. In the majority of these works, the sodium dimer was chosen as an explicit showcase example and the Floquet picture was used to describe the nuclear Hamiltonian. This representation of the Hamiltonian is very illustrative and helps to understand the essence of the light-induced nonadiabatic effects. However, the natural question arises: what are the limits of the Floquet approximation? In this paper, the performance of the 2×2 Floquet Hamiltonian in the space of the ground and resonantly excited molecular electronic states is compared to that of the time-dependent exact Hamiltonian in the same space. For the latter case, we also present results employing the popular rotating wave approximation. To carry out the comparisons, different physical properties---autocorrelation function, excited state diabatic populations and molecular alignment--have been computed [ABSTRACT FROM AUTHOR]

The description of Rydberg states by the complete active space self-consistent field (CASSCF) electronic structure method is known to be a difficult topic. In particular, two problems are frequently encountered: (a) the simultaneous presence of valence and Rydberg excited states in the same energy region can potentially lead to artificial valence–Rydberg mixing in the electronic wave functions. (b) Rydberg states have a tendency to be difficult to converge. We have implemented an approach for the consistent description of both valence and Rydberg excited states within the CASSCF electronic structure model. By employing the multiconfigurational second- and third-order perturbation theory (CASPT2/3) methods based on CASSCF reference wave functions, the procedure is verified by comparison with spectroscopic results for the example molecule pyrazine. Vertical excitation energies and other properties have been calculated for various electronic states. Basis sets and active spaces were selected to provide accurate results. Two combinations of aug-cc-pVTZ level basis sets complemented by Rydberg functions have been employed to calculate estimates for the properties of 19 singlet excited states of pyrazine. While many of the assignments made in previous studies could be confirmed, there are also several new aspects emerging from the present investigation. [ABSTRACT FROM AUTHOR]

The ground and electronically excited singlet states of tetrahydrocannabinol have been studied theoretically using density functional and time-dependent density functional methods. The vertical excitation energies, the equilibrium geometries as well as the adiabatic excitation energies have been determined. Opening of the six-membered ring between the oxygen and carbon atoms has been considered as photochemical reaction path. This mechanism leads to a typical excited-state intramolecular hydrogen-transfer process and produces low-lying S0– S1 intersection (possible conical intersection, CI) which provides a channel for effective radiationless deactivation of the electronically excited state. [ABSTRACT FROM AUTHOR]

Recently we reported a series of numerical simulations proving that it is possible in principle to create an electronic wave packet and subsequent electronic motion in a neutral molecule photoexcited by a UV pump pulse within a few femtoseconds. We considered the ozone molecule: for this system the electronic wave packet leads to a dissociation process. In the present work, we investigate more specifically the time-resolved photoelectron angular distribution of the ozone molecule that provides a much more detailed description of the evolution of the electronic wave packet. We thus show that this experimental technique should be able to give access to observing in real time the creation of an electronic wave packet in a neutral molecule and its impact on a chemical process. [ABSTRACT FROM AUTHOR]