David Picconi

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Verified

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• PhD
• Senior Researcher at Heinrich Heine University Düsseldorf

Efficient photoswitches capable of complete conversion to their metastable isomer are not so common, yet highly desirable for applications in smart materials and devices. Here, we report the photochromic behavior of a series of styryl cyanine photoswitches, all demonstrating high switching efficiency, with some achieving full conversion to the meta...

Efficient photoswitches capable of complete conversion to their metastable isomer are not so common, yet highly desirable for applications in smart materials and devices. Here, we report the photochromic behavior of a series of styryl cyanine photoswitches, all demonstrating high switching efficiency, with some achieving full conversion to the meta...

The photophysics of nucleobases has been the subject of both theoretical and experimental studies over the past decades due to the challenges posed by resolving the steps of their radiationless relaxation dynamics, which cannot be described in the framework of the Born–Oppenheimer approximation (BOA). In this context, the ultrafast dynamics of 2-th...

Quantum-classical methods for nonadiabatic molecular dynamics, based on the Mayer-Miller-Stock-Thoss mapping, are implemented in the open source computer package PySurf. This complements the implementation of surface hopping approaches performed in previous works, and leads to a unified code that allows nonadiabatic dynamics simulations using vario...

Simulating the coupled electronic and nuclear response of a molecule to light excitation requires the application of nonadiabatic molecular dynamics. However, when faced with a specific photophysical or photochemical problem, selecting the most suitable theoretical approach from the wide array of available techniques is not a trivial task. The chal...

Modeling the dynamics of a quantum system coupled to a dissipative environment becomes particularly challenging when the system’s dimensionality is too high to permit the computation of its eigenstates. This problem is addressed by introducing an eigenstate-free formalism, where the open quantum system is represented as a mixture of high-dimensiona...

Molecular‐level understanding of photoinduced processes is critically important for breakthroughs in transformative technologies utilizing light, ranging from photomedicine to photoresponsive materials. Theory and simulation play a crucial role in this task. Despite great advances in hardware and computational methods, the theoretical description o...

We present a comprehensive, combined experimental and theoretical study of the core-level photoelectron and near-edge x-ray absorption fine structure (NEXAFS) spectra of 2-thiouracil, 4-thiouracil, and 2,4-dithiouracil at the oxygen 1s, nitrogen 1s, carbon 1s, and the sulfur 2s and 2p edges. X-ray photoelectron spectra were calculated using equatio...

Following up on our previous work on vibrationally resolved electronic absorption spectra including the effect of vibrational pre-excitation [J. von Cosel et al., J. Chem. Phys. 147, 164116 (2017)], we present a combined theoretical and experimental study of two-photon induced vibronic transitions in polyatomic molecules that are probed in the Vibr...

The photoinduced charge separation in a symmetric donor–acceptor–donor (D–A–D) triad is studied quantum mechanically using a realistic diabatic vibronic coupling model. The model includes a locally excited DA*D state and two charge-transfer states D+A−D and DA−D+ and is constructed according to a procedure generally applicable to semirigid D–A–D st...

We present a comparative study of the gas-phase UV spectra of uracil and its thionated counterparts (2-thiouracil, 4-thiouracil and 2,4-dithiouracil), closely supported by time-dependent density functional theory calculations to assign the transitions observed. We systematically discuss pure gas-phase spectra for the (thio)uracils in the range of 2...

The conversion of photon energy into other energetic forms in molecules is accompanied by charge moving on ultrafast timescales. We directly observe the charge motion at a specific site in an electronically excited molecule using time-resolved x-ray photoelectron spectroscopy (TR-XPS). We extend the concept of static chemical shift from conventiona...

The photoinduced nonadiabatic dynamics of the enol-keto isomerization of 10-hydroxybenzo[h]quinoline (HBQ) are studied computationally using high-dimensional quantum dynamics. The simulations are based on a diabatic vibronic coupling Hamiltonian, which includes the two lowest $$\pi \pi ^*$$ π π ∗ excited states and a $$n\pi ^*$$ n π ∗ state, which...

The photoinduced nonadiabatic dynamics of the enol-keto isomerization of 10-hydroxybenzo[h]quinoline (HBQ) are studied computationally using high dimensional quantum dynamics. The simulations are based on a diabatic vibronic coupling Hamiltonian, which includes the two lowest ππ* excited states and a nπ* state, which has high energy in the Franck-C...

Photoexcited molecules convert photon energy into other energetic degrees of freedom involving the coupling of ultrafast electronic and nuclear motion. Here, we demonstrate that time-resolved x-ray photoelectron spectroscopy (TR-XPS) offers a new way to investigate the molecular photoinduced dynamics based on changes in the local charge at the core...

We present time-resolved ultraviolet-pump x-ray probe Auger spectra of 2-thiouracil. An ultraviolet induced shift towards higher kinetic energies is observed in the sulfur 2p Auger decay. The difference Auger spectra of pumped and unpumped molecules exhibit ultrafast dynamics in the shift amplitude, in which three phases can be recognized. In the f...

This contribution addresses the experimental observation Picconi, D.Burghardt, I. theoretical interpretation of environment-induced decoherence of molecular Schrödinger cat states, as observed for dihalogen molecules embedded in a cryogenic rare gas environment. We specifically address a three-pulse experiment performed on an -krypton system,Piccon...

The multi-state photodynamics following the B 3Πu (0+) ← X 1Σ+g excitation of molecular iodine in crystal krypton are studied quantum mechanically using the Gaussian variant of the multiconfigurational time-dependent Hartree method (G-MCTDH). Calculations are performed using a 9-state 18-dimensional Hamiltonian parametrized via diatomics-in-molecul...

A variational approach for the quantum dynamics of statistical mixtures is developed, which is based upon the representation of the natural states of the mixture in terms of hybrid Gaussian-based Multiconfiguration Time-Dependent Hartree (G-MCTDH) wavefunctions. The method, termed ρG-MCTDH, is combined with a treatment of dissipation and decoherenc...

The molecular dynamics following the electronic BΠu3(0+)⟵XΣg+1 photoexcitation of the iodine molecule embedded in solid krypton are studied quantum mechanically using the Gaussian variant of the multiconfigurational time-dependent Hartree method (G-MCTDH). The accuracy of the Gaussian wave packet approximation is validated against numerically exact...

This study presents quantum dynamical simulations, using the Gaussian-based multiconfigurational time-dependent Hartree (G-MCTDH) method, of time-resolved coherent Raman four-wave-mixing spectroscopic experiments for the iodine molecule embedded in a cryogenic crystal krypton matrix [D. Picconi et al., J. Chem. Phys. 150, 064111 (2019)]. These expe...

This companion paper to [D. Picconi et al., J. Chem. Phys., submitted] presents quantum dynamical simulations, using the Gaussian-based multiconfigurational time-dependent Hartree (G-MCTDH) method, of time-resolved coherent Raman four-wave-mixing spectroscopic experiments for the iodine molecule embedded in a cryogenic crystal krypton matrix. These...

The molecular dynamics following the electronic $B\ ^3\Pi_u\left(0^+\right) \longleftarrow X\ ^1\Sigma_g^+$ photoexcitation of the iodine molecule embedded in solid krypton are studied quantum mechanically using the Gaussian variant of the multiconfigurational time-dependent Hartree method (G-MCTDH). The accuracy of the Gaussian wave packet approxi...

This is a quantum mechanical study of the entanglement between pyrrolyl radical and the H-atom formed in the photodissociation of pyrrole. The parent molecule is photoexcited into the low lying 1πσ∗ states interacting with the ground electronic state via avoided crossings or conical intersections. The entanglement, studied in the time independent a...

The analysis of the total kinetic energy release (TKER) of the photofragments pyrrolyl + H-atom formed in the photodissociation of pyrrole in the low-lying state ¹A2(πσ*) is presented. The TKER distributions contain complementary and often more precise information on the fragmentation process than the broad diffuse absorption spectra. The distribut...

This paper opens a series in which the photochemistry of the two lowest πσ* states of pyrrole and their interaction with each other and with the ground electronic state X̃ are studied using ab initio quantum mechanics. New 24-dimensional potential energy surfaces for the photodissociation of the N–H bond and the formation of the pyrrolyl radical ar...

Fano resonances are predicted to be prominent features of the πσ* photochemistry of pyrrole. The Fano interference leads to distorted absorption bands and internally hot photofragments. The interference, studied using high level ab initio theory and quantum mechanics, is supported by two distinct dynamical scenarios controlled by two exit channel c...

The H-atom photodissociationreaction from the pyridinyl radical (C5H5NH) via the low-lying πσ* excited electronic state is investigated by nonadiabatic time-dependent quantum wave-packet dynamics calculations. A model comprising three electronic states and three nuclear coordinates has been constructed using ab initio multi-configurational self-con...

This paper relates the partial cross section of a continuous optical emission into a given scattering channel of the lower electronic state to the photofragment population. This allows one to infer partial emission cross sections ‘non-optically’ from product state distributions; in computations, explicit construction of exact scattering states is t...

Quantum dynamics at a reactive two-state conical intersection lying outside the Franck-Condon zone is studied for a prototypical reaction of ultraviolet photodissociation of ozone in the Hartley band. The focus is on the vibrational distributions in the two electronic states at intermediate interfragment distances near the intersection. Such interm...

Photodissociation of ozone in the near UV is studied quantum mechanically in two excited electronic states coupled at a conical intersection located outside the Franck-Condon zone. The calculations, performed using recent ab initio PESs, provide an accurate description of the photodissociation dynamics across the Hartley/Huggins absorption bands. T...

We present mixed quantum-classical simulation of the internal conversion between the lowest energy pipi* (S(La)) and npi* (S(n)) excited electronic states in adenine in the gas phase, adopting a quadratic vibronic model (QVC), parametrized with the help of PBE0 density functional calculations. Our approach is based on a hierarchical representation...

We present a computational approach of general applicability to simulate the vibronic lineshapes of absorption and electronic circular dichroism (ECD) spectra in rigid exciton-coupled dimers, based on a time-dependent expression of the spectra and quantum dynamical calculations. We adopt a diabatic model of interacting states localized on the monom...

We present a mixed quantum-classical simulation of the internal conversion between the lowest energy ππ* (SLa) and nπ* (Sn) states in adenine in gas phase, adopting a quadratic vibronic model (QVC), parametrized with the help of PBE0 Density Functional calculations. Our approach is based on a hierarchical representation of the QVC Hamiltonian and a...

We face with the general problem of defining a reduced number of effective collective coordinates to describe accurately the short-time nonadiabatic dynamics of large semirigid systems, amenable to a description in terms of coupled harmonic potential energy surfaces. We present a numeric iterative protocol to define a hierarchical representation of...

A quantum mechanical study of the interplay between the bright ππ*(S(π)) and the dark nπ*(S(n)) excited states of thymine in the gas phase is reported. TD-PBE0 calculations indicate that within a relevant region of the S(π) surface, connecting the Franck-Condon point with the planar and non-planar S(π) plateau, S(π) and S(n) are almost isoenergetic...