A5023671253- Laser-Matter Interactions and Applications
- Mass Spectrometry Techniques and Applications
- Advanced Chemical Physics Studies
- Spectroscopy and Quantum Chemical Studies
- Quantum, superfluid, helium dynamics
- Cold Atom Physics and Bose-Einstein Condensates
- Atomic and Molecular Physics
- Advanced Fiber Laser Technologies
- Laser Design and Applications
- Ion-surface interactions and analysis
- Spectroscopy and Laser Applications
- Meat and Animal Product Quality
- Orbital Angular Momentum in Optics
- Laser-Plasma Interactions and Diagnostics
- Advanced X-ray Imaging Techniques
- Proteins in Food Systems
- Atomic and Subatomic Physics Research
- Advanced Chemical Sensor Technologies
- Laser-induced spectroscopy and plasma
- Microencapsulation and Drying Processes
- Quantum optics and atomic interactions
- Microfluidic and Bio-sensing Technologies
- Molecular spectroscopy and chirality
- Mechanical and Optical Resonators
- Protein Hydrolysis and Bioactive Peptides
Aarhus University
2016-2025
Max Planck Institute for the Study of Societies
2019
University of Oxford
2015-2018
University of California, Berkeley
2018
University of Connecticut
2018
Lund University
2018
Max-Born-Institute for Nonlinear Optics and Short Pulse Spectroscopy
2018
Helmholtz-Zentrum Dresden-Rossendorf
2018
Kansas State University
2018
Oxford Research Group
2016
We review the theoretical and experimental status of intense laser alignment---a field at interface between physics chemical dynamics with potential applications ranging from high harmonic generation nanoscale processing to stereodynamics control reactions. After placing approach in context other alignment techniques, we proceed a discussion underlying this technique description methods observing it laboratory. The roles played by frequency, pulse duration, system temperature are illustrated...
A strong inhomogeneous static electric field is used to spatially disperse a supersonic beam of polar molecules, according their quantum state. We show that the molecules residing in lowest-lying rotational states can be selected and as targets for further experiments. As an illustration, we demonstrate unprecedented degree laser-induced one-dimensional alignment $(⟨{cos}^{2}{\ensuremath{\theta}}_{2\mathrm{D}}⟩=0.97)$ orientation state-selected iodobenzene molecules. This method should...
We report experimental results on x-ray diffraction of quantum-state-selected and strongly aligned ensembles the prototypical asymmetric rotor molecule 2,5-diiodobenzonitrile using Linac Coherent Light Source. The experiments demonstrate first steps toward a new approach to diffractive imaging distinct structures individual, isolated gas-phase molecules. confirm several key ingredients single experiments: abilities detect count individual scattered photons in shot data, deliver...
We demonstrate, theoretically and experimentally, that an intense, elliptically polarized, nonresonant laser field can simultaneously force all three axes of a molecule to align along given fixed in space, thus inhibiting the free rotation Euler angles. Theoretically, effect is illustrated through time dependent quantum mechanical calculations. Experimentally, 3, 4-dibromothiophene molecules are aligned with nanosecond pulse. The alignment probed by 2D ion imaging fragments from 20 fs pulse...
A strong nonresonant nanosecond laser pulse is used to align neutral iodine molecules. The technique, applicable both polar and nonpolar molecules, relies on the interaction between field induced dipole moment of degree alignment enhanced by lowering initial rotational energy molecules or increasing intensity. measured photodissociating with a femtosecond detecting direction photofragments imaging techniques. strongest observed 〈cos2 θ〉=0.81.
Using ultrashort pulse multiphoton ionization, we launch a wave packet in the ${\mathrm{I}}_{2}^{\phantom{\rule{0ex}{0ex}}2+}$ state that dissociates into fragments ${\mathrm{I}}^{2+}$ and I. We measure its ionization probability as function of internuclear distance with an intense delayed probe pulse. If is polarized parallel to axis, observe peak yield at critical 5--6 \AA{}. No such enhancement seen perpendicular polarization agreement model enhanced by electron localization.
Molecules in a seeded supersonic beam are aligned by the interaction between an intense nonresonant linearly polarized laser field and molecular polarizability. We demonstrate general applicability of scheme aligning I2, ICl, CS2, CH3I, C6H5I molecules. The alignment is probed mass selective two dimensional imaging photofragment ions produced femtosecond pulses. Calculations on degree I2 good agreement with experiments. discuss some future applications
The ac Stark shift produced by nonresonant radiation creates a potential minimum for ground state molecule at the position where laser intensity is maximum. gradient of this exerts force on molecule. We experimentally observe when beam ${\mathrm{CS}}_{2}$ molecules redirected sending it through near focus beam. trace direction in molecular beam, showing that pass center high will focus.
Ionization and fragmentation of methylselenol (CH(3)SeH) molecules by intense (>10(17) W/cm(2)) 5 fs x-ray pulses (ħω=2 keV) are studied coincident ion momentum spectroscopy. We contrast the measured charge state distribution with data on atomic Kr, determine kinetic energies resulting ionic fragments, compare them to outcome a Coulomb explosion model. find signatures ultrafast redistribution from inner-shell ionized Se atom its molecular partners, observe significant displacement...
Recording molecular movies on ultrafast timescales has been a longstanding goal for unravelling detailed information about dynamics. Here we present the direct experimental recording of very-high-resolution and -fidelity over more than one-and-a-half periods laser-induced rotational dynamics carbonylsulfide (OCS) molecules. Utilising combination single quantum-state selection an optimised two-pulse sequence to create tailored wavepacket, unprecedented degree field-free alignment, 〈cos2θ2D〉 =...
We show experimentally that field-free alignment of iodobenzene molecules, induced by a single, intense, linearly polarized 1.4-ps-long laser pulse, can be strongly enhanced dividing the pulse into two optimally synchronized pulses same duration. For given total energy two-pulse sequence degree is maximized with an intensity ratio 1:3 and sending second near time where created first peaks.
The motion and dimension of molecular nuclear wave packets produced by an ultrashort laser pulse are measured Coulomb explosion induced a delayed intense fs pulse. Two different continuum in ${\mathrm{I}}_{2}$ observed as they move from internuclear separation $\ensuremath{\sim}7$ to $>100$ \AA{}. ultimate spatial resolution is limited the duration probe laser. For 485 nm excitation $B$-state limit $\ensuremath{\sim}0.5$
Supersonic beams of polar molecules are deflected using inhomogeneous electric fields. The quantum-state selectivity the deflection is used to spatially separate according their quantum state. A detailed analysis and obtained selection presented. rotational temperatures molecular determined from spatial beam profiles all approximately 1 K. Unprecedented degrees laser-induced alignment (<cos2 theta2D>=0.972) orientation iodobenzene demonstrated when state-selected samples used. Such oriented...
We demonstrate that strong laser pulses can induce torsional motion in a molecule consisting of pair phenyl rings. A nanosecond pulse spatially aligns the carbon-carbon bond axis, connecting two rings, allowing perpendicularly polarized, intense femtosecond to initiate accompanied by an overall rotation about fixed axis. monitor induced time-resolved Coulomb explosion imaging. Our theoretical analysis accounts for and generalizes experimental findings.
Laser-aligned carbondisulfide (CS2) molecules are singly ionized by multiphoton absorption from intense, linearly polarized 25 fs laser pulses. The angular distribution of the photoelectrons exhibits a significant dependence on angle between polarizations aligning and ionizing fields. widely used strong-field approximation predicts distributions in qualitative agreement with experimental data but fails at quantitative level.
A strong inhomogeneous static electric field is used to spatially disperse a rotationally cold supersonic beam of 2,6-difluoroiodobenzene molecules according their rotational quantum state. The in the lowest lying states are selected and as targets for 3-dimensional alignment orientation. induced adiabatic regime with an elliptically polarized, intense laser pulse orientation by combined action weak field. We show that degree strongly enhanced when state-selected molecules, rather than...
We demonstrate an experimental method to record snapshot diffraction images of polyatomic gas-phase molecules, which can, in a next step, be used probe time-dependent changes the molecular geometry during photochemical reactions with femtosecond temporal and angstrom spatial resolution. Adiabatically laser-aligned 1-ethynyl-4-fluorobenzene (C${}_{8}$H${}_{5}$F) molecules were imaged by photoelectrons kinetic energies between 31 62 eV, created from core ionization fluorine ($1s$) level...
We study how the combination of long and short laser pulses, can be used to induce torsion in an axially chiral biphenyl derivative (3,5-difluoro-3',5'-dibromo-4'-cyanobiphenyl). A long, with respect molecular rotational periods, elliptically polarized pulse produces 3D alignment molecules, a linearly initiates about stereogenic axis. The torsional motion is monitored real-time by measuring dihedral angle using femtosecond time-resolved Coulomb explosion imaging. Within first 4 picoseconds,...
We show that a 450 fs nonresonant, moderately intense, linearly polarized laser pulse can induce field-free molecular axis alignment of methyliodide (${\mathrm{CH}}_{3}\mathrm{I}$) molecules dissolved in helium nanodroplet. Time-resolved measurements reveal rotational dynamics much slower than isolated and absence the sharp transient recurrences characteristic gas phase molecules. Our results presage range new opportunities for exploring both dissipative environment properties He nanodroplets.
A nanosecond laser pulse confines the spatial orientation of naphthalene in 1D or 3D while a femtosecond kick initiates rotation molecular plane around fixed long axis. Time-dependent photoelectron angular distributions (PADs), resulting from ionization by an intense probe pulse, exhibit pronounced changes as rotates. Enhanced alignment, occurring shortly after provides strongly improved contrast molecular-frame PADs. Calculations strong-field approximation show that striking structures...
The yield of strong-field ionization, by a linearly polarized probe pulse, is studied experimentally and theoretically, as function the relative orientation between laser field molecule. Experimentally, carbonyl sulfide, benzonitrile naphthalene molecules are aligned in one or three dimensions before being singly ionized 30 fs pulse centered at 800 nm. Theoretically, we address behaviour these molecules. We consider degree alignment model angular dependence total ionization molecular...
The torsional motion of a molecule composed two substituted benzene rings, linked by single bond, is coherently controlled pair strong ($3\ifmmode\times\else\texttimes\fi{}1{0}^{13}\text{ }\text{ }\mathrm{W}\text{ }{\mathrm{cm}}^{\ensuremath{-}2}$), nonresonant (800 nm) 200-fs-long laser pulses---both linearly polarized perpendicular to the single-bond axis. If second pulse sent at time when rings rotate toward (away from) each other amplitude torsion strongly enhanced (reduced). persists...