# DrVitaliAverbukh

Faculty of Natural SciencesDepartment of Physics

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### Contact

+44 (0)20 7594 7746v.averbukh

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### Location

209Blackett LaboratorySouth Kensington Campus

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## Publications

Publication Type
Year
to

82 results found

Tarrant J, Khokhlova M, Averbukh V, 2022, Interferometry of Quantum Revivals, The Journal of Chemical Physics, ISSN: 0021-9606

<jats:p> It has recently been shown that an interferometric approach can be used to obtain Auger lifetimes in molecules in certain point groups. Here, we extend this concept to those molecular states for which Auger decay is energetically forbidden and which exhibit initial quasi-exponential decay followed by quantum revivals. We demonstrate that this allows us to extract the quasi-exponential decay rate and the revival timescale. We solve analytically a model containing a state coupled to the idealised Bixon-Jortner quasicontinuum, and we obtain an interferometric signature of revival which can be easily generalised to realistic systems. Moreover, we analyse how this revival signature is influenced by the system parameters, and we suggest optimal conditions for its observation. We therefore show that our new approach allows population revivals of a molecular state to be detected interferometrically. </jats:p>

Journal article

Schwickert D, Ruberti M, Kolorenc P, Usenko S, Przystawik A, Baev K, Baev I, Braune M, Bocklage L, Czwalinna MK, Deinert S, Duesterer S, Hans A, Hartmann G, Haunhorst C, Kuhlmann M, Palutke S, Roehlsberger R, Roensch-Schulenburg J, Schmidt P, Toleikis S, Viefhaus J, Martins M, Knie A, Kip D, Averbukh V, Marangos JP, Laarmann Tet al., 2022, Electronic quantum coherence in glycine molecules probed with ultrashort x-ray pulses in real time, SCIENCE ADVANCES, Vol: 8, ISSN: 2375-2548

Journal article

Li S, Driver T, Rosenberger P, Champenois EG, Duris J, Al-Haddad A, Averbukh V, Barnard JCT, Berrah N, Bostedt C, Bucksbaum PH, Coffee RN, DiMauro LF, Fang L, Garratt D, Gatton A, Guo Z, Hartmann G, Haxton D, Helml W, Huang Z, LaForge AC, Kamalov A, Knurr J, Lin M-F, Lutman AA, MacArthur JP, Marangos JP, Nantel M, Natan A, Obaid R, O'Neal JT, Shivaram NH, Schori A, Walter P, Li Wang A, Wolf TJA, Zhang Z, Kling MF, Marinelli A, Cryan JPet al., 2022, Attosecond coherent electron motion in Auger-Meitner decay, SCIENCE, Vol: 375, Pages: 285-+, ISSN: 0036-8075

Journal article

Driver T, Bachhawat N, Pipkorn R, Frasinski LJ, Marangos JP, Edelson-Averbukh M, Averbukh Vet al., 2021, Proteomic Database Search Engine for Two-Dimensional Partial Covariance Mass Spectrometry, ANALYTICAL CHEMISTRY, Vol: 93, Pages: 14946-14954, ISSN: 0003-2700

Journal article

Bray AC, Maxwell AS, Kissin Y, Ruberti M, Ciappina MF, Averbukh V, Faria CFDMet al., 2021, Polarization in strong-field ionization of excited helium, JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, Vol: 54, ISSN: 0953-4075

Journal article

Barillot T, Alexander O, Cooper B, Driver T, Garratt D, Li S, Al Haddad A, Sanchez-Gonzalez A, Agåker M, Arrell C, Bearpark MJ, Berrah N, Bostedt C, Bozek J, Brahms C, Bucksbaum PH, Clark A, Doumy G, Feifel R, Frasinski LJ, Jarosch S, Johnson AS, Kjellsson L, Kolorenč P, Kumagai Y, Larsen EW, Matia-Hernando P, Robb M, Rubensson J-E, Ruberti M, Sathe C, Squibb RJ, Tan A, Tisch JWG, Vacher M, Walke DJ, Wolf TJA, Wood D, Zhaunerchyk V, Walter P, Osipov T, Marinelli A, Maxwell TJ, Coffee R, Lutman AA, Averbukh V, Ueda K, Cryan JP, Marangos JPet al., 2021, Correlation-driven transient hole dynamics resolved in space and time in the isopropanol molecule, Physical Review X, Vol: 11, Pages: 1-15, ISSN: 2160-3308

The possibility of suddenly ionized molecules undergoing extremely fast electron hole (or, hole)dynamics prior to significant structural change was first recognized more than 20 years ago andtermed charge migration. The accurate probing of ultrafast electron hole dynamics requires measurements that have both sufficient temporal resolution and can detect the localization of a specifichole within the molecule. We report an investigation of the dynamics of inner valence hole states inisopropanol where we use an x-ray pump/x-ray probe experiment, with site and state-specific probing of a transient hole state localized near the oxygen atom in the molecule, together with an abinitio theoretical treatment. We record the signature of transient hole dynamics and make the firsttentative observation of dynamics driven by frustrated Auger-Meitner transitions. We verify thatthe effective hole lifetime is consistent with our theoretical prediction. This state-specific measurement paves the way to widespread application for observations of transient hole dynamics localizedin space and time in molecules and thus to charge transfer phenomena that are fundamental inchemical and material physics.

Journal article

Driver T, Averbukh V, Frasiński LJ, Marangos JP, Edelson-Averbukh Met al., 2021, Two-dimensional partial covariance mass spectrometry for the top-down analysis of intact proteins., Analytical Chemistry, Vol: 93, Pages: 10779-10788, ISSN: 0003-2700

Two-dimensional partial covariance mass spectrometry (2D-PC-MS) exploits the inherent fluctuations of fragment ion abundances across a series of tandem mass spectra, to identify correlated pairs of fragment ions produced along the same fragmentation pathway of the same parent (e.g., peptide) ion. Here, we apply 2D-PC-MS to the analysis of intact protein ions in a standard linear ion trap mass analyzer, using the fact that the fragment-fragment correlation signals are much more specific to the biomolecular sequence than one-dimensional (1D) tandem mass spectrometry (MS/MS) signals at the same mass accuracy and resolution. We show that from the distribution of signals on a 2D-PC-MS map it is possible to extract the charge state of both parent and fragment ions without resolving the isotopic envelope. Furthermore, the 2D map of fragment-fragment correlations naturally separates the products of the primary decomposition pathways of the molecular ions from those of the secondary ones. We access this spectral information using an adapted version of the Hough transform. We demonstrate the successful identification of highly charged, intact protein molecules bypassing the need for high mass resolution. Using this technique, we also perform the in silico deconvolution of the overlapping fragment ion signals from two co-isolated and co-fragmented intact proteins, demonstrating a viable new method for the concurrent mass spectrometric identification of a mixture of intact protein ions from the same fragment ion spectrum.

Journal article

Driver T, Bachhawat N, Frasinski L, Marangos J, Averbukh V, Edelson-Averbukh Met al., 2021, Chimera spectrum diagnostics for peptides using two-dimensional partial covariance mass spectrometry, Molecules, Vol: 26, ISSN: 1420-3049

The rate of successful identification of peptide sequences by tandem mass spectrometry (MS/MS) is adversely affected by the common occurrence of co-isolation and co-fragmentation of two or more isobaric or isomeric parent ions. This results in so-called `chimera spectra’, which feature peaks of the fragment ions from more than a single precursor ion. The totality of the fragment ion peaks in chimera spectra cannot be assigned to a single peptide sequence, which contradicts a fundamental assumption of the standard automated MS/MS spectra analysis tools, such as protein database search engines. This calls for a diagnostic method able to identify chimera spectra to single out the cases where this assumption is not valid. Here, we demonstrate that, within the recently developed two-dimensional partial covariance mass spectrometry (2D-PC-MS), it is possible to reliably identify chimera spectra directly from the two-dimensional fragment ion spectrum, irrespective of whether the co-isolated peptide ions are isobaric up to a finite mass accuracy or isomeric. We introduce ‘3-57 chimera tag’ technique for chimera spectrum diagnostics based on 2D-PC-MS and perform numerical simulations to examine its efficiency. We experimentally demonstrate the detection of a mixture of two isomeric parent ions, even under conditions when one isomeric peptide is at one five-hundredth of the molar concentration of the second isomer.

Journal article

Kissin Y, Ruberti M, Kolorenc P, Averbukh Vet al., 2021, Attosecond pump-attosecond probe spectroscopy of Auger decay, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 23, Pages: 12376-12386, ISSN: 1463-9076

Journal article

Driver T, Cooper B, Ayers R, Pipkorn R, Patchkovskii S, Averbukh V, Klug D, Marangos J, Frasinski L, Edelson-Averbukh Met al., 2020, Two-dimensional partial covariance mass spectrometry of large molecules based on fragment correlations, Physical Review X, Vol: 10, Pages: 041004 – 1-041004 – 13, ISSN: 2160-3308

Covariance mapping [L. J. Frasinski, K. Codling, and P. A. Hatherly, Science 246, 1029 (1989)] is a well-established technique used for the study of mechanisms of laser-induced molecular ionization and decomposition. It measures statistical correlations between fluctuating signals of pairs of detected species (ions, fragments, electrons). A positive correlation identifies pairs of products originating from the same dissociation or ionization event. A major challenge for covariance-mapping spectroscopy is accessing decompositions of large polyatomic molecules, where true physical correlations are overwhelmed by spurious signals of no physical significance induced by fluctuations in experimental parameters. As a result, successful applications of covariance mapping have so far been restricted to low-mass systems, e.g., organic molecules of around 50 daltons (Da). Partial-covariance mapping was suggested to tackle the problem of spurious correlations by taking into account the independently measured fluctuations in the experimental conditions. However, its potential has never been realized for the decomposition of large molecules, because in these complex situations, determining and continuously monitoring multiple experimental parameters affecting all the measured signals simultaneously becomes unfeasible. We introduce, through deriving theoretically and confirming experimentally, a conceptually new type of partial-covariance mapping—self-correcting partial-covariance spectroscopy—based on a parameter extracted from the measured spectrum itself. We use the readily available total ion count as the self-correcting partial-covariance parameter, thus eliminating the challenge of determining experimental parameter fluctuations in covariance measurements of large complex systems. The introduced self-correcting partial covariance enables us to successfully resolve correlations of molecules as large as

Journal article

Khokhlova M, Bahmanpour L, Bachhawat N, Cooper B, Averbukh Vet al., 2020, Interatomic coulombic decay rate in endohedral complexes, JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, Vol: 53, ISSN: 0953-4075

Journal article

Kolorenc P, Averbukh V, 2020, Fano-ADC(2,2) method for electronic decay rates, JOURNAL OF CHEMICAL PHYSICS, Vol: 152, ISSN: 0021-9606

Journal article

Driver T, Li S, Champenois EG, Duris J, Ratner D, Lane TJ, Rosenberger P, Al-Haddad A, Averbukh V, Barnard T, Berrah N, Bostedt C, Bucksbaum PH, Coffee R, DiMauro LF, Fang L, Garratt D, Gatton A, Guo Z, Hartmann G, Haxton D, Helml W, Huang Z, LaForge A, Kamalov A, Kling MF, Knurr J, Lin M-F, Lutman AA, MacArthur JP, Marangos JP, Nantel M, Natan A, Obaid R, O'Neal JT, Shivaram NH, Schori A, Walter P, Wang AL, Wolf TJA, Marinelli A, Cryan JPet al., 2020, Attosecond transient absorption spooktroscopy: a ghost imaging approach to ultrafast absorption spectroscopy, Physical Chemistry Chemical Physics, Vol: 22, Pages: 2704-2712, ISSN: 1463-9076

The recent demonstration of isolated attosecond pulses from an X-ray free-electron laser (XFEL) opens the possibility for probing ultrafast electron dynamics at X-ray wavelengths. An established experimental method for probing ultrafast dynamics is X-ray transient absorption spectroscopy, where the X-ray absorption spectrum is measured by scanning the central photon energy and recording the resultant photoproducts. The spectral bandwidth inherent to attosecond pulses is wide compared to the resonant features typically probed, which generally precludes the application of this technique in the attosecond regime. In this paper we propose and demonstrate a new technique to conduct transient absorption spectroscopy with broad bandwidth attosecond pulses with the aid of ghost imaging, recovering sub-bandwidth resolution in photoproduct-based absorption measurements.

Journal article

Khokhlova M, Cooper B, Ueda K, Prince KC, Kolorenc P, Ivanov M, Averbukh Vet al., 2020, Molecular Auger Interferometry, 31st International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC), Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588

Conference paper

Bray AC, Maxwell AS, Faria CFDM, Kissin Y, Ruberti M, Khokhlova M, Averbukh Vet al., 2020, Polarisation Effects in Above-Threshold Ionisation of Excited Helium, 31st International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC), Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588

Conference paper

Khokhlova MA, Cooper B, Ueda K, Prince KC, Kolorenc P, Ivanov MY, Averbulch Vet al., 2019, Molecular Auger Interferometry, Physical Review Letters, Vol: 122, ISSN: 0031-9007

We introduce and present a theory of interferometric measurement of a normal Auger decay lifetime in molecules. Molecular Auger interferometry is based on the coherent phase control of Auger dynamics in a two-color (ω/2ω) laser field. We show that, in contrast to atoms, in oriented molecules of certain point groups the relative ω/2ω phase modulates the total ionization yield. A simple analytical formula is derived for the extraction of the lifetimes of Auger-active states from a molecular Auger interferogram, circumventing the need in either high-resolution or attosecond spectroscopy. We demonstrate the principle of the interferometric Auger lifetime measurement using inner-valence decay in CH3F.

Journal article

Ruberti M, Decleva P, Averbukh V, 2018, Full Ab Initio Many-Electron Simulation of Attosecond Molecular Pump-Probe Spectroscopy., J Chem Theory Comput

Here, we present an ab initio approach to full simulation of an attosecond molecular pump-probe experiment. Sequential molecular double ionization by the pump and probe laser pulses with controlled delay is described from first-principles with a full account of the continuum dynamics of the photoelectrons. Many-electron bound-continuum dynamics is simulated using the time-dependent (TD) molecular B-spline algebraic diagrammatic construction (ADC) method. Our calculations give a quantitative prediction about the creation of a coherent superposition of molecular ionic states in the photoionization process and simulate the probe of the ensuing attosecond dynamics by a second ionizing pulse within a single first-principles many-electron framework. We therefore demonstrate the capability to simulate and interpret the results of a prototypical molecular pump-probe experiment of interest in attoscience. As a particular example, we simulate and elucidate the interpretation of a pump-probe experiment in CO2 aimed at measuring strong field-induced hole dynamics via photoionization yields.

Journal article

Averbukh V, Ruberti M, 2018, First-principles many-electron dynamics using the B-spline algebraic diagrammatic construction approach, Attosecond Molecular Dynamics, Editors: Vrakking, Lepine, Vrakking, Lepine, Publisher: Royal Society of Chemistry, Pages: 68-102, ISBN: 9781782629955

In this chapter we present a first-principles theoretical and numerical method based on the many-electron algebraic diagrammatic construction [ADC(n)] schemes for electronic excitations, able to describe the correlated multi-electron ionisation dynamics induced in atomic and molecular systems by laser pulses both in the perturbative and non-perturbative regime. Within the ADC(n) framework, electron correlation is described at different levels of approximation depending on the specific ADC method n used within the ADC hierarchy. An accurate representation of the electronic ionisation continuum is achieved by the implementation and computational optimisation of the first- [ADC(1)] and second-order [ADC(2)] schemes in the monocentric B-spline basis set, which makes it possible to describe highly oscillatory discretised continuum wave-functions. The implementation of the time-dependent version of the B-spline ADC method is made by solving the many-electron time-dependent Schrödinger equation via the Arnoldi Lanczos algorithm. As illustrative examples we present applications of this method to the calculations of both static quantities (photoionisation cross sections of noble gas atoms) and dynamical quantities such as the high harmonic generation spectra of Ar and CO2, and the attosecond transient absorption spectrum in laser dressed He atoms.

Book chapter

Yun R, Narevicius E, Averbukh V, 2018, Penning ionization widths by Fano-algebraic diagrammatic construction method, Journal of Chemical Physics, Vol: 148, ISSN: 0021-9606

We present an ab initio theory and computational method for Penning ionization widths. Our method is based on the Fano theory of resonances, algebraic diagrammatic construction (ADC) scheme for many-electron systems, and Stieltjes imaging procedure. It includes an extension of the Fano-ADC scheme [V. Averbukh and L. S. Cederbaum, J. Chem. Phys. 123, 204107 (2005)] to triplet excited states. Penning ionization widths of various He*-H2states are calculated as a function of the distance R between He* and H2. We analyze the asymptotic (large-R) dependences of the Penning widths in the region where the well-established electron transfer mechanism of the decay is suppressed by the multipole- and/or spin-forbidden energy transfer. The R-12and R-8power laws are derived for the asymptotes of the Penning widths of the singlet and triplet excited states of He*(1s2s1,3S), respectively. We show that the electron transfer mechanism dominates Penning ionization of He*(1s2s3S)-H2up until the He*-H2separation is large enough for the radiative decay of He* to become the dominant channel. The same mechanism also dominates the ionization of He*(1s2s1S)-H2when R < 5 Å. We estimate that the regime of energy transfer in the He*-H2Penning ionization cannot be reached by approaching zero collisional temperature. However, the multipole-forbidden energy transfer mechanism can become important for Penning ionization in doped helium droplets.

Journal article

Ruberti M, Decleva P, Averbukh V, 2018, Multi-channel dynamics in high harmonic generation of aligned CO₂: ab initio analysis with time-dependent B-spline algebraic diagrammatic construction, Physical Chemistry Chemical Physics, Vol: 20, Pages: 8311-8325, ISSN: 1463-9076

Here we present a fully ab initio study of the high-order harmonic generation (HHG) spectrum of aligned CO2 molecules. The calculations have been performed by using the molecular time-dependent (TD) B-spline algebraic diagrammatic construction (ADC) method. We quantitatively study how the sub-cycle laser-driven multi-channel dynamics, as reflected in the position of the dynamical minimum in the HHG spectrum, is affected by the full inclusion of both correlation-driven and laser-driven dipole interchannel couplings. We calculate channel-resolved spectral intensities as well as the phase differences between contributions of the different ionization-recombination channels to the total HHG spectrum. Our results show that electron correlation effectively controls the relative contributions of the different channels to the total HHG spectrum, leading to the opening of the new ones (12Πu, 12Σ), previously disregarded for the aligned molecular setup. We conclude that inclusion of many-electron effects into the theoretical interpretation of molecular HHG spectra is essential in order to correctly extract ultrafast electron dynamics using HHG spectroscopy.

Journal article

Cooper B, Girdlestone S, Burovskiy P, Gaydadjiev G, Averbukh V, Knowles PJ, Luk Wet al., 2017, Quantum Chemistry in Dataflow: Density-Fitting MP2., Journal of Chemical Theory and Computation, Vol: 13, Pages: 5265-5272, ISSN: 1549-9618

We demonstrate the use of dataflow technology in the computation of the correlation energy in molecules at the Møller-Plesset perturbation theory (MP2) level. Specifically, we benchmark density fitting (DF)-MP2 for as many as 168 atoms (in valinomycin) and show that speed-ups between 3 and 3.8 times can be achieved when compared to the MOLPRO package run on a single CPU. Acceleration is achieved by offloading the matrix multiplications steps in DF-MP2 to Dataflow Engines (DFEs). We project that the acceleration factor could be as much as 24 with the next generation of DFEs.

Journal article

Neville SP, Averbukh V, Ruberti M, Yun R, Patchkovskii S, Chergui M, Stolow A, Schuurman MSet al., 2016, Excited state X-ray absorption spectroscopy: Probing both electronic and structural dynamics, JOURNAL OF CHEMICAL PHYSICS, Vol: 145, ISSN: 0021-9606

Journal article

Neville SP, Averbukh V, Patchkovskii S, Ruberti M, Yun R, Chergui M, Stolow A, Schuurman MSet al., 2016, Beyond structure: ultrafast X-ray absorption spectroscopy as a probe of non-adiabatic wavepacket dynamics., Faraday Discussions, ISSN: 1364-5498

The excited state non-adiabatic dynamics of polyatomic molecules, leading to the coupling of structural and electronic dynamics, is a fundamentally important yet challenging problem for both experiment and theory. Ongoing developments in ultrafast extreme vacuum ultraviolet (XUV) and soft X-ray sources present new probes of coupled electronic-structural dynamics because of their novel and desirable characteristics. As one example, inner-shell spectroscopy offers localized, atom-specific probes of evolving electronic structure and bonding (via chemical shifts). In this work, we present the first on-the-fly ultrafast X-ray time-resolved absorption spectrum simulations of excited state wavepacket dynamics: photo-excited ethylene. This was achieved by coupling the ab initio multiple spawning (AIMS) method, employing on-the-fly dynamics simulations, with high-level algebraic diagrammatic construction (ADC) X-ray absorption cross-section calculations. Using the excited state dynamics of ethylene as a test case, we assessed the ability of X-ray absorption spectroscopy to project out the electronic character of complex wavepacket dynamics, and evaluated the sensitivity of the calculated spectra to large amplitude nuclear motion. In particular, we demonstrate the pronounced sensitivity of the pre-edge region of the X-ray absorption spectrum to the electronic and structural evolution of the excited-state wavepacket. We conclude that ultrafast time-resolved X-ray absorption spectroscopy may become a powerful tool in the interrogation of excited state non-adiabatic molecular dynamics.

Journal article

Simpson ER, Sanchez-Gonzalez A, Austin DR, Diveki Z, Hutchinson SEE, Siegel T, Ruberti M, Averbukh V, Miseikis L, Strüber CS, Chipperfield L, Marangos JPet al., 2016, Polarisation response of delay dependent absorption modulation in strong field dressed helium atoms probed near threshold, New Journal of Physics, Vol: 18, ISSN: 1367-2630

Wepresent the first measurement of the vectorial response of strongly dressed helium atoms probed by an attosecond pulse train (APT) polarised either parallel or perpendicular to the dressing field polarisation. The transient absorption is probed as a function of delay between the APT and the Linearly polarised 800 nmfield of peak intensity 1.3∗1014 W cm-2. The APT spans the photon energy range 1642 eV, covering the first ionisation energy of helium (24.59 eV). With parallel polarised dressing and probing fields, we observe modulations with periods of one half and one quarter of the dressing field period. When the polarisation of the dressing field is altered from parallel to perpendicular with respect to the APT polarisation we observe a large suppression in the Modulation depth of the above ionisation threshold absorption. In addition to this we present the intensity dependence of the harmonic modulation depth as a function of delay between the dressing and probe fields, with dressing field peak intensities ranging from 2∗1012 to 2∗1014 W cm-2.We compare our experimental results with a full-dimensional solution of the single-atom time-dependent (TD) Schrdinger equation obtained using the recently developed abinitio TDB-spline ADCmethod and find good qualitative agreement for the above threshold harmonics.

Journal article

Kolorenc P, Averbukh V, Feifel R, Eland Jet al., 2016, Collective relaxation processes in atoms, molecules and clusters, Journal of Physics B-Atomic Molecular and Optical Physics, Vol: 49, ISSN: 1361-6455

Electron correlation is an essential driver of a variety of relaxation processes in excited atomic and molecular systems. These are phenomena which often lead to autoionization typically involving two-electron transitions, such as the well-known Auger effect. However, electron correlation can give rise also to higher-order processes characterized by multi-electron transitions. Basic examples include simultaneous two-electron emission upon recombination of an inner-shell vacancy (double Auger decay) or collective decay of two holes with emission of a single electron. First reports of this class of processes date back to the 1960s, but their investigation intensified only recently with the advent of free-electron lasers. High fluxes of high-energy photons induce multiple excitation or ionization of a system on the femtosecond timescale and under such conditions the importance of multi-electron processes increases significantly. We present an overview of experimental and theoretical works on selected multi-electron relaxation phenomena in systems of different complexity, going from double Auger decay in atoms and small molecules to collective interatomic autoionization processes in nanoscale samples.

Journal article

Feifel R, Eland JHD, Squibb RJ, Mucke M, Zagorodskikh S, Linusson P, Tarantelli F, Kolorenc P, Averbukh Vet al., 2016, Ultrafast Molecular Three-Electron Auger Decay, PHYSICAL REVIEW LETTERS, Vol: 116, ISSN: 0031-9007

Journal article

Simpson ER, Sanchez-Gonzalez A, Austin DR, Diveki Z, Hutchinson SEE, Siegel T, Ruberti M, Averbukh V, Miseikis L, Strüber C, Chipperfield L, Marangos JPet al., 2015, The response of a neutral atom to a strong laser field probed by transient absorption near the ionisation threshold

We present transient absorption spectra of an extreme ultraviolet attosecondpulse train in helium dressed by an 800 nm laser field with intensity rangingfrom $2\times10^{12}$ W/cm$^2$ to $2\times10^{14}$ W/cm$^2$. The energy rangeprobed spans 16-42 eV, straddling the first ionisation energy of helium (24.59eV). By changing the relative polarisation of the dressing field with respectto the attosecond pulse train polarisation we observe a large change in themodulation of the absorption reflecting the vectorial response to the dressingfield. With parallel polarized dressing and probing fields, we observesignificant modulations with periods of one half and one quarter of thedressing field period. With perpendicularly polarized dressing and probingfields, the modulations of the harmonics above the ionisation threshold aresignificantly suppressed. A full-dimensionality solution of the single-atomtime-dependent Schr\"odinger equation obtained using the recently developedab-initio time-dependent B-spline ADC method reproduce some of ourobservations.

Working paper

Sanchez-Gonzalez A, Barillot TR, Squibb RJ, Kolorenc P, Agaker M, Averbukh V, Bearpark MJ, Bostedt C, Bozek JD, Bruce S, Montero SC, Coffee RN, Cooper B, Cryan JP, Dong M, Eland JHD, Fang L, Fukuzawa H, Guehr M, Ilchen M, Johnsson AS, Liekhus-S C, Marinelli A, Maxwell T, Motomura K, Mucke M, Natan A, Osipov T, Ostlin C, Pernpointner M, Petrovic VS, Robb MA, Sathe C, Simpson ER, Underwood JG, Vacher M, Walke DJ, Wolf TJA, Zhaunerchyk V, Rubensson J-E, Berrah N, Bucksbaum PH, Ueda K, Feifel R, Frasinski LJ, Marangos JPet al., 2015, Auger electron and photoabsorption spectra of glycine in the vicinity of the oxygen K-edge measured with an X-FEL, JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, Vol: 48, ISSN: 0953-4075

Journal article

Shagam Y, Klein A, Skomorowski W, Yun R, Averbukh V, Koch CP, Narevicius Eet al., 2015, Molecular hydrogen interacts more strongly when rotationally excited at low temperatures leading to faster reactions, Nature Chemistry, Vol: 7, Pages: 921-926, ISSN: 1755-4330

The role of internal molecular degrees of freedom, such as rotation, has scarcely been explored experimentally in low-energy collisions despite their significance to cold and ultracold chemistry. Particularly important to astrochemistry is the case of the most abundant molecule in interstellar space, hydrogen, for which two spin isomers have been detected, one of which exists in its rotational ground state whereas the other is rotationally excited. Here we demonstrate that quantization of molecular rotation plays a key role in cold reaction dynamics, where rotationally excited ortho-hydrogen reacts faster due to a stronger long-range attraction. We observe rotational state-dependent non-Arrhenius universal scaling laws in chemi-ionization reactions of para-H2 and ortho-H2 by He(23P2), spanning three orders of magnitude in temperature. Different scaling laws serve as a sensitive gauge that enables us to directly determine the exact nature of the long-range intermolecular interactions. Our results show that the quantum state of the molecular rotor determines whether or not anisotropic long-range interactions dominate cold collisions.

Journal article

Schnorr K, Senftleben A, Schmid G, Augustin S, Kurka M, Rudenko A, Foucar L, Broska A, Meyer K, Anielski D, Boll R, Rolles D, Kuebel M, Kling MF, Jiang YH, Mondal S, Tachibana T, Ueda K, Marchenko T, Simon M, Brenner G, Treusch R, Scheit S, Averbukh V, Ullrich J, Pfeifer T, Schroeter CD, Moshammer Ret al., 2015, Time-resolved study of ICD in Ne dimers using FEL radiation, JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA, Vol: 204, Pages: 245-256, ISSN: 0368-2048

Journal article

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