Sequential and direct ionic excitation in the strong-field ionization of 1-butene molecules

We study the Strong-Field Ionization (SFI) of the hydrocarbon 1-butene as a function of wavelength using photoion-photoelectron covariance and coincidence spectroscopy. We observe a striking transition in the fragment-associated photoelectron spectra: from a single Above Threshold Ionization (ATI) progression for photon energies less than the cation D0–D1 gap to two ATI progressions for a photon energy greater than this gap. For the first case, electronically excited cations are created by SFI populating the ground cationic state D0, followed by sequential post-ionization excitation. For the second case, direct sub-cycle SFI to the D1 excited cation state contributes significantly. Our experiments access ionization dynamics in a regime where strong-field and resonance-enhanced processes can interplay

Following the excited state relaxation dynamics of indole and 5-hydroxyindole using time-resolved photoelectron spectroscopy

Time-resolved photoelectron spectroscopy was used to obtain new information about the dynamics of electronic relaxation in gas-phase indole and 5-hydroxyindole following UV excitation with femtosecond laser pulses centred at 249 nm and 273 nm. Our analysis of the data was supported by ab initio calculations at the coupled cluster and complete-active-space self-consistent-field levels. The optically bright 1La and 1Lb electronic states of 1\u3c0\u3c0* character and spectroscopically dark and dissociative 1\u3c0\u3c3* states were all found to play a role in the overall relaxation process. In both molecules we conclude that the initially excited 1La state decays non-adiabatically on a sub 100 fs timescale via two competing pathways, populating either the subsequently long-lived 1Lb state or the 1\u3c0\u3c3* state localised along the N-H coordinate, which exhibits a lifetime on the order of 1 ps. In the case of 5-hydroxyindole, we conclude that the 1\u3c0\u3c3* state localised along the O-H coordinate plays little or no role in the relaxation dynamics at the two excitation wavelengths studied.Peer reviewed: YesNRC publication: Ye

Fixação zigomática em portadores de fissura de lábio e palato: relato de caso clínico

A técnica de Fixação Zigomática serve como um meio alternativo para pacientes que apresentam grande perda de estrutura maxilar decorrentes de atrofia maxilar severa, traumas, cirurgias ressectivas tumorais ou defeitos congênitos. Pacientes portadores de fissura de lábio e palato podem ser beneficiados com esta técnica, pois apresentam baixo desenvolvimento de seus maxilares devido às cirurgias primárias de queiloplastia e palatoplastia. O implante zigomático de titânio que possui em média 30 mm a 52,5 mm de comprimento, se insere no rebordo alveolar remanescente em direção ao corpo do zigoma. Por meio dessa técnica, é possível ancorar uma prótese fixa utilizando carga precoce. Objetivo: O objetivo deste trabalho foi de relatar um caso ocorrido no Hospital de Reabilitação de Anomalias Craniofaciais, Bauru, São Paulo, com resolução protética de um paciente portador de fissura labiopalatina através da ancoragem zigomática. Relato Clínico: Em 2008, paciente do Hospital de Reabilitação de Anomalias Craniofaciais, portadora de fissura labiopalatina, foi realizado um planejamento criterioso e a opção mais adequada foi a resolução protética através de uma ancoragem em zigoma. Foi utilizado implante zigomático do lado direito e implantes unitários na região dos dos elementos dentários 13 e 11, após exodontia do elemento 11. Assim, confeccionada uma prótese sobre implantes e placa miorrelaxante com controle de 45 dias. Conclusão: Esta alternativa possibilita ao paciente uma menor morbidade, sem a necessidade de cirurgias de reconstrução óssea, apresenta um tempo menor de tratamento e consequentemente integrando o paciente à sociedade.Disponível em CD-Rom. Acesso ao resumo

Author correction: femtosecond laser mass spectrometry and high harmonic spectroscopy of xylene isomers

1 pags. -- Correction to: Scientific Reports https://doi.org/10.1038/s41598-018-22055-9, published online 28 February 2018A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.Peer reviewe

Pacemaker implantation through pericardial reflections under fluoroscopic guidance: a novel approach for patients with limited venous access

Excited state intramolecular proton transfer (ESIPT) in salicylideneaniline (SA) and selected derivatives substituted in para-position of the anilino group has been investigated by femtosecond time-resolved photoelectron spectroscopy (TRPES) and time-dependent density functional theory (TDDFT). The planarity of the molecule was found to be a key parameter to describe ESIPT

Substituent effects on dynamics at conical intersections : Cyclopentadienes

Substituent effects on dynamics at conical intersections are investigated by means of femtosecond timeresolved photoelectron spectroscopy for cyclopentadiene and its substituted analogues 1,2,3,4-tetramethylcyclopentadiene, 1,2,3,4,5-pentamethylcyclopentadiene, and 1,2,3,4-tetramethyl-5-propylcyclopentadiene. By UV excitation to the S2 (11B2) state, the influence of these substitutions on dynamics for the initially excited S2 (11B2) surface and the spectroscopically dark S1 (21A1) surface were investigated. We observed that the dynamics depend only on a small number of specific vibrations. Whereas dynamics at the S2/S1-conical intersection are independent of substitution at the 5-position, internal conversion dynamics on the S1 (21A1) surface slow down as the inertia of the 5-substituent increases. Contrary to the expectations of simple models of radiationless transitions, an increasing density of states does not lead to faster processes, suggesting that a true dynamical picture of vibrational motions at conical intersections will be required.Peer reviewed: YesNRC publication: Ye

Two-photon excited state dynamics of dark valence, rydberg, and superexcited states in 1,3-butadiene

Two-photon absorption in systems with parity permits access to states that cannot be prepared by one-photon absorption. Here we present the first time-resolved photoelectron spectroscopy study using this technique, applied to 1,3-butadiene, in which we investigated the dynamics of its dark valence, Rydberg, and superexcited states. The dark valence state dynamics are accessed via the Rydberg manifold, excited by two photons of 400 nm. We find that the 'dark' 21Ag state populated in this manner has a much longer lifetime than when accesses via the 11Bu 'bright' valence state when populated by one photon of 200 nm. In addition, we compared the dynamics of the 3s\u3c0- and 3d\u3c0-Rydberg states. These Rydberg states relax to the valence manifold on a subpicosecond time scale, with the 3s\u3c0-Rydberg state decay rate being larger due to a stronger valence-Rydberg mixing. Finally, we investigated superexcited valence states that fragment or autoionize within 200 fs, likely without involving Rydberg states.Peer reviewed: YesNRC publication: Ye

Through-bond interactions and the localization of excited-state dynamics

The influence of through-bond interactions on nonadiabatic excited-state dynamics is investigated by time-resolved photoelectron spectroscopy (TRPES) and ab initio computation. We compare the dynamics of cyclohexa-1,4-diene, which exhibits a through-bond interaction known as homoconjugation (the electronic correlation between nonconjugated double bonds), with the nonconjugated cyclohexene. Each molecule was initially excited to a 3s Rydberg state using a 200 nm femtosecond pump pulse. The TRPES spectra of these molecules display similar structure and time constants on a subpicosecond time scale. Our ab initio calculations show that similar sets of conical intersections (a [1,2]- and [1,3]-hydrogen shift, as well as carbon\u2013carbon bond cleavage) are energetically accessible to both molecules and that the geometry and orbital composition at the minimum energy crossing points to the ground state are directly analogous. These experimental and computational results suggest that the excited-state dynamics of cyclohexa-1,4-diene become localized at a single double bond and that the effects of through-bond interaction, dominant in the absorption spectrum, are absent in the excited-state dynamics. The notion of excited-state dynamics being localized at specific sites within the nuclear framework is analogous to the localization of light absorption by a subsystem within the molecule, designated a chromophore. We propose the utility of the analogous concept, denoted here as a dynamophore.Peer reviewed: YesNRC publication: Ye

Non-Born-Oppenheimer wavepacket dynamics in polyatomic molecules: vibrations at conical intersections in DABCO

The role of vibrational dynamics in the vicinity of conical intersections is investigated using the first two electronically excited states of 1,4-diazabicyclo[2,2,2]octane (DABCO) by combining time-resolved photoelectron spectroscopy with ab initio computation. Upon resonant excitation of the origin band of the short-lived S2 (1E\u2032) state, oscillations in the electronic population between the S2 (1E\u2032) and the S1 (1A\u20321) electronic states are observed with a period of 3 ps. Ab initio computations are employed to characterise these low-lying excited states, which arise from single excitations into the 3s and 3p Rydberg orbitals. Although Rydberg states are generally only weakly coupled, DABCO exhibits rapid nonadiabatic dynamics. This implies that strong coupling occurs only in the immediate vicinity of a conical intersection, enabling unique identification of those vibrations which generate the nonadiabatic transitions. To this end, seams of conical intersection are located at energetically relevant geometries, engendered by differential distortions of the S1 and S2 potentials due to vibronic coupling and a Jahn\u2013Teller-distorted S2 minimum energy point. From an analysis of the conical intersection topography, those vibrations leading to a maximal modulation of the coupling between the electronic states are readily identified. The observed oscillation in the decay of S2 state population is thereby assigned to the beat frequency between two sets of vibronic eigenstates within the S1 manifold, coherently prepared together with another set at the S2 band origin, and whose nominal e\u2032 degeneracy is lifted due to differential coupling to the Jahn\u2013Teller-distorted components of S2.Peer reviewed: YesNRC publication: Ye