Kasra Amini

Kasra Amini
Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy | MBI · Division A: Attosecond Physics

Oxford University, DPhil (PhD) Physical and Theoretical Chemistry
Junior Group Leader at Max Born Institute, Berlin. My group is focussed on ultrafast electron diffraction and CEI work.

About

43
Publications
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476
Citations

Publications

Publications (43)
Article
Full-text available
The ultraviolet (UV)-induced dissociation and photofragmentation of gas-phase CH 2 BrI molecules induced by intense femtosecond extreme ultraviolet (XUV) pulses at three different photon energies are studied by multi-mass ion imaging. Using a UV-pump — XUV-probe scheme, charge transfer between highly charged iodine ions and neutral CH 2 Br radicals...
Article
Full-text available
Ultrafast diffraction imaging is a powerful tool to retrieve the geometric structure of gas-phase molecules with combined picometre spatial and attosecond temporal resolution. However, structural retrieval becomes progressively difficult with increasing structural complexity, given that a global extremum must be found in a multi-dimensional solutio...
Article
Full-text available
Supersonic jets of gas-phase atoms and small molecules have enabled a variety of ultrafast and ultracold chemical studies. However, extension to larger, more complex neutral molecules proves challenging for two reasons: (i) Complex molecules, such as cis-stilbene, exist in a liquid or solid phase at room temperature and ambient pressure and (ii) a...
Preprint
Full-text available
Ultrafast diffraction imaging is a powerful tool to retrieve the geometric structure of gas-phase molecules with combined picometre spatial and attosecond temporal resolution. However, structural retrieval becomes progressively difficult with increasing structural complexity, given that a global extremum must be found in a multi-dimensional solutio...
Article
Full-text available
The interference of matter waves is one of the intriguing features of quantum mechanics that has impressed researchers and laymen since it was first suggested almost a century ago. Nowadays, attosecond science tools allow us to utilize it in order to extract valuable information from electron wave packets. Intense laser fields are routinely employe...
Preprint
Full-text available
Ubiquitous to most molecular scattering methods is the challenge to retrieve bond distance and angle from the scattering signals since this requires convergence of pattern matching algorithms or fitting methods. This problem is typically exacerbated when imaging larger molecules or for dynamic systems with little a priori knowledge. Here, we employ...
Preprint
Full-text available
We report the design and implementation of multiple Tesla type micro valves in the target delivery system of a reaction microscope (ReMi) to study gas phase structural dynamics of complex polyatomic molecules, when no delivery system currently exists that can deliver dense enough molecular jets of neutral complex molecules without ionizing or excit...
Preprint
Full-text available
The interference of matter waves is one of the intriguing features of quantum mechanics that has impressed researchers and laymen since it was first suggested almost a century ago. Nowadays, attosecond science tools allow us to utilize it in order to extract valuable information from electron wavepackets. Intense laser fields are routinely employed...
Article
Full-text available
Visualizing molecular transformations in real-time requires a structural retrieval method with Ångström spatial and femtosecond temporal atomic resolution. Imaging of hydrogen-containing molecules additionally requires an imaging method sensitive to the atomic positions of hydrogen nuclei, with most methods possessing relatively low sensitivity to...
Preprint
Full-text available
Visualizing molecular transformations in real-time requires a structural retrieval method with {\AA}ngstr\"om spatial and femtosecond temporal atomic resolution. Imaging of hydrogen-containing molecules additionally requires an imaging method that is sensitive to the atomic positions of hydrogen nuclei, with most methods possessing relatively low s...
Chapter
Full-text available
Knowledge of molecular structure is paramount in understanding, and ultimately influencing, chemical reactivity. For nearly a century, diffractive imaging has been used to identify the structures of many biologically-relevant gas-phase molecules with atomic (i.e., Ångstrom, Å; 1 Å = 10− 10 m) spatial resolution. Unraveling the mechanisms of chemica...
Article
Full-text available
Synopsis We use laser-induced electron diffraction (LIED) to self-image the molecular structure of an isolated water molecular ion using its own retuning attosecond electron wave packet (EWP). Using LIED’s sub-femtosecond and picometre spatio-temporal resolution imaging capabilities, we observe the symmetric stretching of the O-H and H-H internucle...
Article
Full-text available
Synopsis We present experimental results of linear-to-bent transition of field-dressed molecules, mediated by Renner-Teller effect. Using the state-of-the-art laser-induced electron diffraction (LIED) technique, we image a bent and symmetrically stretched carbon disulfide (CS 2 ) molecule populating an excited electronic state under the influence o...
Article
Full-text available
We publish three Roadmaps on photonic, electronic and atomic collision physics in order to celebrate the 60th anniversary of the ICPEAC conference. In Roadmap I, we focus on the light–matter interaction. In this area, studies of ultrafast electronic and molecular dynamics have been rapidly growing, with the advent of new light sources such as attos...
Article
Full-text available
Observing changes in molecular structure requires atomic-scale Ångstrom and femtosecond spatio-temporal resolution. We use the Fourier transform (FT) variant of laser-induced electron diffraction (LIED), FT-LIED, to directly retrieve the molecular structure of H2O⁺ with picometer and femtosecond resolution without a priori knowledge of the molecula...
Article
Full-text available
This paper has been prepared by the Symphony collaboration (University of Warsaw, Uniwersytet Jagielloński, DESY/CNR and ICFO) on the occasion of the 25th anniversary of the "simple man's models" which underlie most of the phenomena that occur when intense ultrashort laser pulses interact with matter. The phenomena in question include High-Harmonic...
Preprint
Full-text available
Observing changes in molecular structure requires atomic-scale Ångstrom and femtosecond spatio-temporal resolution. We use the Fourier transform (FT) variant of laser-induced electron diffraction (LIED), FT-LIED, to directly retrieve the molecular structure of H2O + with picometre and femtosecond resolution without a priori knowledge of the molecul...
Preprint
Full-text available
Observing changes in molecular structure requires atomic-scale {\AA}ngstrom and femtosecond spatio-temporal resolution. We use the Fourier transform (FT) variant of laser-induced electron diffraction (LIED), FT-LIED, to directly retrieve the molecular structure of ${\rm H_2O^+}$ with picometre and femtosecond resolution without a priori knowledge o...
Preprint
Full-text available
This paper has been prepared by the Symphony collaboration (University of Warsaw, Uniwersytet Jagiello\'nski, DESY/CNR and ICFO) on the occasion of the 25th anniversary of the "simple man's models" which underlie most of the phenomena that occur when intense ultrashort laser pulses interact with matter. The phenomena in question include High-Harmon...
Article
Full-text available
The photodissociation dynamics of CH3I and CH2ClI at 272 nm were investigated by time-resolved Coulomb explosion imaging, with an intense non-resonant 815 nm probe pulse. Fragment ion momenta over a wide m/z range were recorded simultaneously by coupling a velocity map imaging spectrometer with a pixel imaging mass spectrometry camera. For both mol...
Preprint
Altering the geometric structure of a polyatomic molecule by populating an excited electronic state is one possible mechanism that can influence chemical reactivity and is often utilized in photochemical reactions. Although excited state structures can be prepared and subsequently measured using pump-probe techniques and high-resolution rotational...
Article
Due to its element and site specificity, inner-shell photoelectron spectroscopy is a widely used technique to probe the chemical structure of matter. Here, we show that time-resolved inner-shell photoelectron spectroscopy can be employed to observe ultrafast chemical reactions and the electronic response to the nuclear motion with high sensitivity....
Cover Page
Full-text available
“Communication: Gas-phase structural isomer identification by Coulomb explosion of aligned molecules,” has been featured on the cover of The Journal of Chemical Physics.
Article
Full-text available
The dynamics following laser-induced molecular photodissociation of gas-phase CH$_{2}$BrI at 271.6 nm were investigated by time-resolved Coulomb explosion imaging using intense near-IR femtosecond laser pulses. The observed delay-dependent photofragment momenta reveal that CH$_{2}$BrI undergoes C-I cleavage, depositing 65.6% of the available energy...
Article
Full-text available
We explore time-resolved Coulomb explosion induced by intense, extreme ultraviolet (XUV) femtosecond pulses from the FLASH free-electron laser as a method to image photo-induced molecular dynamics in two molecules, iodomethane and difluoroiodobenzene. At an excitation wavelength of 267 nm, the dominant reaction pathway in both molecules is neutral...
Article
Full-text available
Laser-induced adiabatic alignment and mixed-field orientation of 2,6-difluoroiodobenzene (C6H3F2I) molecules are probed by Coulomb explosionimaging following either near-infrared strong-field ionization or extreme-ultraviolet multi-photoninner-shell ionization using free-electron laser pulses. The resulting photoelectrons and fragment ions are capt...
Article
The fragmentation dynamics of 2,6- and 3,5-difluoroiodobenzene after iodine 4d inner-shell photoionization with soft X-rays are studied using coincident electron and ion momentum imaging. By analyzing the momentum correlation between iodine and fluorine cations in three-fold ion coincidence events, we can distinguish the two isomers experimentally....
Article
Full-text available
In pump-probe experiments employing a free-electron laser (FEL) in combination with a synchronized optical femtosecond laser, the arrival-time jitter between the FEL pulse and the optical laser pulse often severely limits the temporal resolution that can be achieved. Here, we present a pump-probe experiment on the UV-induced dissociation of 2,6-dif...
Article
Full-text available
The fragmentation dynamics of 2,6- and 3,5-difluoroiodobenzene after iodine 4$d$ inner-shell photoionization with soft X-rays are studied using coincident electron and ion momentum imaging. By analyzing the momentum correlation between iodine and fluorine cations in three-fold ion coincidence events, we can distinguish the two isomers experimentall...
Article
Full-text available
We apply a three-fold covariance imaging method to analyse previously acquired data [C. S. Slater et al., Phys. Rev. A 89, 011401(R) (2014)] on the femtosecond laser-induced Coulomb explosion of spatially pre-aligned 3,5-dibromo-3',5'-difluoro-4'-cyanobiphenyl molecules. The data were acquired using the "Pixel Imaging Mass Spectrometry" camera. We...
Article
Full-text available
The Pixel Imaging Mass Spectrometry (PImMS) camera is used in proof-of-principle three-dimensional imaging experiments on the photodissociation of carbonyl sulfide and ethyl iodide at wavelengths around 230 nm and 245 nm, respectively. Coupling the PImMS camera with DC-sliced velocity-map imaging allows the complete three-dimensional Newton sphere...

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Projects

Projects (3)
Project
To elucidate the structure and ultrafast molecular dynamics of gaseous polyatomic molecules using the few-picometre and sub-femtosecond spatio-temporal resolution of the LIED method. A home-built 3.2 micron OPCPA set-up coupled with a reaction microscope enables a full electron-ion coincidence imaging of a single molecule. This paves the way for directly recording the ultimate super high resolution molecular movie.
Project
Laser-induced Coulomb explosion of molecules has been utilized to track the kinetic energy and angular distributions of the recoil ions to gauge structural and dynamical information on the parent molecule and any associated photo-induced chemical reactions.