Imaging CF
            <sub>3</sub>
            I conical intersection and photodissociation dynamics with ultrafast electron diffraction

Yang, Jie; Zhu, Xiaolei; Wolf, Thomas; Li, Zheng; Nunes, João; Coffee, Ryan; Cryan, James; Gühr, Markus; Hegazy, Kareem; Heinz, Tony F.; Jobe, K.; Li, Renkai; Shen, Xiaozhe; Veccione, Theodore; Weathersby, Stephen; Wilkin, Kyle; Yoneda, Charles; Zheng, Qiang; Martı́nez, Todd J.; Centurion, Martin; Wang, Xijie

doi:10.1126/science.aat0049

Cited by 217 publications

(199 citation statements)

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“…The UED experiment reported here was carried out using the MeV UED setup at SLAC, sketched in Fig. 3 and described elsewhere in detail [23]. Briefly, the electron and laser beam are approximately collinear as they traverse a gas jet containing C2F4I2 molecules.…”

Section: Methodsmentioning

confidence: 99%

“…Although UED experiments in condensed matter samples were able to reach femtosecond resolution [19], in gas phase experiments the resolution had been limited to the picosecond timescale, mainly by the velocity mismatch between laser and electron pulses. Recently, it has become possible to achieve femtosecond resolution in gas phase UED using relativistic (MeV) electron pulses [20], with first experiments that observed rotational and vibrational nuclear wavepackets in diatomic molecules [21,22] and recent experiments that captured the dynamics in more complex reactions such as the passage of a nuclear wavepacket through a conical intersection and ringopening dynamics [23,24]. Here we use UED to investigate the prompt photo-dissociation of C 2F4I2, the formation of the C2F4I radical and the subsequent coherent dynamics in the electronic ground state.…”

Section: Introduction a Backgroundmentioning

confidence: 99%

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Diffractive imaging of dissociation and ground-state dynamics in a complex molecule

et al. 2019

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We have investigated the structural dynamics in photoexcited 1,2-diiodotetrafluoroethane molecules (C2F4I2) in the gas phase experimentally using ultrafast electron diffraction and theoretically using FOMO-CASCI excited state dynamics simulations. The molecules are excited by an ultra-violet femtosecond laser pulse to a state characterized by a transition from the iodine 5p⊥ orbital to a mixed 5p|| σ hole and CF2  antibonding orbital, which results in the cleavage of one of the carbon-iodine bonds. We have observed, with sub-Angstrom resolution, the motion of the nuclear wavepacket of the dissociating iodine atom followed by coherent vibrations in the electronic ground state of the C2F4I radical. The radical reaches a stable classical (nonbridged) structure in less than 200 fs. I.

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Section: Methodsmentioning

confidence: 99%

Section: Introduction a Backgroundmentioning

confidence: 99%

Diffractive imaging of dissociation and ground-state dynamics in a complex molecule

et al. 2019

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“…It is highly desired (in particular for those experiments that require long data acquisition time (see, e.g. [21])) if the beam can be compressed without increasing the jitter such that time-stamping technique is not needed. Many efforts have been devoted towards this goal in the past few years.…”

Section: Pacs Numbersmentioning

confidence: 99%

Femtosecond Relativistic Electron Beam with Reduced Timing Jitter from THz Driven Beam Compression

Zhao

Tang

et al. 2020

Phys. Rev. Lett.

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We propose and demonstrate a novel method to reduce the pulse width and timing jitter of a relativistic electron beam through THz-driven beam compression. In this method the longitudinal phase space of a relativistic electron beam is manipulated by a linearly polarized THz pulse in a dielectric tube such that the bunch tail has a higher velocity than the bunch head, which allows simultaneous reduction of both pulse width and timing jitter after passing through a drift. In this experiment, the beam is compressed by more than a factor of four from 130 fs to 28 fs with the arrival time jitter also reduced from 97 fs to 36 fs, opening up new opportunities in using pulsed electron beams for studies of ultrafast dynamics. This technique extends the well known rf buncher to the THz frequency and may have a strong impact in accelerator and ultrafast science facilities that require femtosecond electron beams with tight synchronization to external lasers. PACS numbers:Ultrashort electron beams with small timing jitter with respect to external lasers are of fundamental interest in accelerator and ultrafast science communities. For instance, such beams are essential for laser and THz-driven accelerators ([1-4]) where the beam energy spread and beam energy stability largely depend on the electron bunch length and injection timing jitter, respectively. For MeV ultrafast electron diffraction (UED [5-12]) where ultrashort electron beams with a few MeV energy are used to probe the atomic structure changes following the excitation of a pump laser, the temporal resolution is primarily limited by the electron bunch length and timing jitter. Similar limitations exist for x-ray free-electron lasers ) too, since the properties of the x-ray pulses depend primarily on that of the electron beams. Therefore, one of the long-standing goals in accelerator and ultrafast science communities is to generate ultrashort electron beams with small timing jitter.Photocathode rf gun is the leading option for producing high brightness ultrashort electron beam for FEL and MeV UED (see, e.g. [16,17]). Due to space charge effect, the electron beam pulse width is broadened and therefore bunch compression is typically needed to reduce the pulse width. Bunch compression requires first a mechanism to imprint energy chirp (correlation between an electron's energy and its longitudinal position) and then sending the beam through a dispersive element such that the longitudinal displacement of the electrons is changed in a controlled way for reducing the pulse width. For MeV beam, this is typically achieved by first sending the beam through a rf buncher cavity at zero-crossing phase where the bunch head (t < 0) is decelerated while the bunch tail (t > 0) is accelerated. This imprints a negative chirp h = dδ/cdt < 0 in the beam longitudinal phase space, where δ is the relative energy difference of an electron with respect to the reference electron and c is the speed of light. Then the electron beam is sent through a drift after which the electrons at the bunch tail...

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“…In particular, theoretical approaches and experimental measurements have made use of UV‐pump/X‐ray‐probe schemes to identify different dissociation paths in CF 4 and SF 6 molecules . Time‐resolved diffraction experiments performed with X‐ray FEL pulses have also been able to capture a real‐time image of the dynamics through a conical intersection in CF 3 I …”

Section: Molecular Attosecond Dynamicsmentioning

confidence: 99%

The quantum chemistry of attosecond molecular science

Palacios

Martı́n

2019

WIREs Comput Mol Sci

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With the advent of attosecond light pulses at the beginning of this century, the possibility to perform real-time observations of electron motion in molecules has spurred impressive theoretical developments aimed at providing support and guidance to numerous, but still incipient, experimental efforts devoted to understand chemistry at its ultimate temporal frontier: the attosecond. The first real-time observation of electron dynamics in a relatively large molecule, phenylalanine, was reported in 2014. This would have been difficult without the help of theory, since observations in this emerging field, recently coined attochemistry, are still indirect.While standard Quantum Chemistry methods can describe excited bound-state dynamics, new approaches incorporating scattering theory formalisms are needed to understand the interaction with attosecond pulses. Indeed, due to their short wavelengths, lying in the XUV and X-ray spectral regions, the interaction of such pulses with any molecule inevitably leads to ionization, which requires describing the molecular ionization continuum. Also, because of their short duration (i.e., large bandwidth), ionization is accompanied by the formation of a molecular electronic wave packet (i.e., a coherent superposition of electronic states), which evolves in time and dictates the fate of the molecule at the longer time scales where chemistry shows up. Although much has already been done up to date, current bottlenecks in the field are to account for electron correlations during the ionization process and for the coupled electron and nuclear dynamics that follows. Past and ongoing theoretical efforts are described here along with experimental work towards the solid establishment of attochemistry. This article is categorized under: Electronic Structure Theory > Ab Initio Electronic Structure Methods Software > Quantum Chemistry Theoretical and Physical Chemistry > Spectroscopy K E Y W O R D S attochemistry, attosecond dynamics, molecular dynamics, molecular ionization, ultrafast

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Imaging CF ₃ I conical intersection and photodissociation dynamics with ultrafast electron diffraction

Cited by 217 publications

References 58 publications

Diffractive imaging of dissociation and ground-state dynamics in a complex molecule

Diffractive imaging of dissociation and ground-state dynamics in a complex molecule

Femtosecond Relativistic Electron Beam with Reduced Timing Jitter from THz Driven Beam Compression

The quantum chemistry of attosecond molecular science

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Imaging CF 3 I conical intersection and photodissociation dynamics with ultrafast electron diffraction

Cited by 217 publications

References 58 publications

Diffractive imaging of dissociation and ground-state dynamics in a complex molecule

Diffractive imaging of dissociation and ground-state dynamics in a complex molecule

Femtosecond Relativistic Electron Beam with Reduced Timing Jitter from THz Driven Beam Compression

The quantum chemistry of attosecond molecular science

Contact Info

Product

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Imaging CF ₃ I conical intersection and photodissociation dynamics with ultrafast electron diffraction