A5075656844- Laser-Matter Interactions and Applications
- Advanced Chemical Physics Studies
- Mass Spectrometry Techniques and Applications
- Electron and X-Ray Spectroscopy Techniques
- Spectroscopy and Quantum Chemical Studies
- Nuclear Physics and Applications
- Spectroscopy and Laser Applications
- Lanthanide and Transition Metal Complexes
- Photochemistry and Electron Transfer Studies
- X-ray Spectroscopy and Fluorescence Analysis
- Advanced Fiber Laser Technologies
- Chemical Reactions and Isotopes
- Laser Design and Applications
- Advanced Electron Microscopy Techniques and Applications
- Medical Imaging Techniques and Applications
- Mechanical and Optical Resonators
- Inorganic and Organometallic Chemistry
- Molecular Sensors and Ion Detection
- Ion-surface interactions and analysis
- Photonic Crystal and Fiber Optics
- Radiopharmaceutical Chemistry and Applications
- Photocathodes and Microchannel Plates
- bioluminescence and chemiluminescence research
- Augmented Reality Applications
- Analytical Chemistry and Sensors
National Research Council Canada
2016-2025
Steacie Institute for Molecular Sciences
2011-2020
University of Ottawa
2010-2019
Hungarian Academy of Sciences
2019
HUN-REN Wigner Research Centre for Physics
2019
University College London
2017-2019
Stony Brook University
2019
University of Oxford
2017
Helmholtz-Zentrum Berlin für Materialien und Energie
2017
California Institute of Technology
2014
We demonstrate a new method to investigate the origin of spectral structures in high-harmonic generation. report detailed measurements spectra aligned nitrogen and carbon dioxide molecules. Varying wavelength intensity generating laser field, we show that minimum N2 molecules is nearly unaffected, whereas CO2 shifts over more than 15 eV. Our quantitative analysis shows both interference multiple orbitals their structural characteristics affect position minimum. provides simple approach...
Electrons detached from atoms or molecules by photoionization carry information about the quantum state which they originate, as well continuum states into are released. Generally, photoelectron momentum distribution is composed of a coherent sum angular components, each with an amplitude and phase. Here we show, using neon, that train attosecond pulses synchronized infrared laser field can be used to disentangle these components. Two-color, two-photon ionization via Stark-shifted...
Time-resolved photoelectron spectroscopy (TRPES) is a powerful tool for the study of intramolecular dynamics, particularly excited state non-adiabatic dynamics in polyatomic molecules. Depending on problem at hand, different levels TRPES measurements can be performed: time-resolved yield; time- and energy-resolved time-, energy-, angle-resolved yield. In this pedagogical overview, conceptual framework photoionization presented, together with discussion relevant theory aspects TRPES. Simple...
Time-delays in the photoionization of molecules are investigated. As compared to atomic ionization, time-delays expected from molecular ionization present a much richer phenomenon, with strong spatial dependence due anisotropic nature scattering potential. We investigate this theory perspective, and make use calculations examine effect representative homonuclear hetronuclear diatomic molecules, nitrogen carbon monoxide. energy angle-resolved maps Wigner delay time for single-photon valence...
We bring the methodology of orienting polar molecules together with phase sensitivity high harmonic spectroscopy to experimentally compare difference attosecond bursts radiation emitted upon electron recollision from different ends a molecule. This has an impact on harmonics aligned molecules, suppressing emission parallel driving laser field while favoring perpendicular ones. For oriented we measure amplitude ratio even odd produced when intense light irradiates CO and determine degree...
In this work we investigate quantum-enhanced target detection in the presence of large background noise using multidimensional quantum correlations between photon pairs generated through spontaneous parametric down-conversion. Until now similar experiments have only utilized one pairs' many degrees freedom such as temporal and number correlations. Here, both spectral achieved over an order magnitude reduction to turn significant data acquisition time when compared utilizing modes. We believe...
Molecular frame high-harmonic spectra of aligned ${\mathrm{N}}_{2}$ molecules reveal a Cooper-like minimum. By deconvolving the laboratory alignment distribution, what was previously thought to be maximum emission along molecular axis is found maxima at 35 degrees off axis, with spectral minimum on axis. Both these features are supported by photoionization calculations that underline relationship between spectroscopy and measurements. The arises from destructive interference $p$ $f$ partial...
The detailed understanding of electronic coherence in quantum systems requires measurements on the attosecond timescale. Attosecond x-ray pulses enable study core-excited molecular systems. Here we report coherent motion electrons 1,1-difluoroethylene ion following ionization <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>K</a:mi></a:math> shell two nonequivalent carbon sites with a subfemtosecond pulse. Using angular streaking technique to track Auger-Meitner...
Photoelectron angular distributions (PADs) obtained from ionization of potassium atoms using moderately intense femtosecond IR fields (∼10^{12} W cm^{-2}) various polarization states are shown to provide a route "complete" photoionization experiments. Ionization occurs by net three-photon absorption process, driven via the 4s→4p resonance at one-photon level. A theoretical treatment incorporating intrapulse electronic dynamics allows for full set matrix elements be extracted 2D imaging data....
Photoionization of molecular species is, essentially, a multipath interferometer with both experimentally controllable and intrinsic characteristics. In this work, XUV photoionization impulsively aligned targets (N_{2}) is used to provide time-domain route "complete" experiments, in which the rotational wave packet controls geometric part interferometer. The data obtained sufficient determine magnitudes phases ionization matrix elements for all observed channels, reconstruct frame...
The combination of computer simulations and two powerful experimental methods for following molecular change on femtosecond timescales offers an unprecedented view how a photoexcited molecule breaks apart.
We present results from an experimental ion imaging study into the fragmentation dynamics of 1-iodopropane and 2-iodopropane following interaction with extreme ultraviolet intense femtosecond laser pulses a photon energy 95 eV. Using covariance analysis, range observed pathways resulting polycations can be isolated interrogated in detail at relatively high count rates (∼12 ions shot-1). By incorporating recently developed native frames analysis approach three-dimensional procedure,...
Recent developments in X-ray free-electron lasers have enabled a novel site-selective probe of coupled nuclear and electronic dynamics photoexcited molecules, time-resolved photoelectron spectroscopy (TRXPS). We present results from joint experimental theoretical TRXPS study the well-characterized ultraviolet photodissociation CS2, prototypical system for understanding non-adiabatic dynamics. These demonstrate that sulfur 2p binding energy is sensitive to changes structure following...
Abstract Structural imaging of transient excited-state species is a key goal molecular physics, promising to unveil rich information about the dynamics underpinning photochemical transformations. However, separating electronic and nuclear contributions spectroscopic observables challenging, typically requires application high-level theory. Here, we employ site-selective ionisation via ultrashort soft X-ray pulses time-resolved Coulomb explosion interrogate structural ultraviolet...
We present, for the first time, rotationally resolved photoelectron images resulting from ionization of a polyatomic molecule. Photoelectron angular distributions pertaining to formation individual rotational levels $\mathrm{NH}_{3}{}^{+}$ have been extracted and analyzed enable complete determination radial dipole matrix elements relative phases that describe dynamics. This leads deduction significantly different dynamics those in previous studies which lacked either information or resolution.
We report results of the application a fully ab initio approach for simulating time-resolved molecular-frame photoelectron angular distributions around conical intersections in ${\mathrm{CS}}_{2}$. The technique employs wave packet densities obtained with multiple spawning method conjunction geometry- and energy-dependent photoionization matrix elements. robust agreement these measured ${\mathrm{CS}}_{2}$ demonstrates that this can successfully elucidate, disentangle, underlying nuclear...
Angle-resolved (AR) RABBIT measurements offer a high information content measurement scheme, due to the presence of multiple, interfering, ionization channels combined with phase-sensitive observable in form angle and time-resolved photoelectron interferograms. In order explore characteristics potentials AR-RABBIT, perturbative 2-photon model is developed; based on this model, example AR-RABBIT results are computed for real systems, range schemes. These indicate some phenomena be expected...
We compare the excited state dynamics of diiodomethane (CH2I2) and bromoiodomethane (CH2BrI) using time resolved photoelectron spectroscopy. A 4.65 eV UV pump pulse launches a dissociative wave packet on states both molecules ensuing are probed via photoionization 7.75 probe pulse. The resulting photoelectrons measured with velocity map imaging technique for each pump-probe delay. Our measurements highlight differences in two molecules, which interpreted high-level ab initio molecular...
C-I bond extension and fission following ultraviolet (UV, 262 nm) photoexcitation of 2- 3-iodothiophene is studied using ultrafast time-resolved extreme (XUV) ionization in conjunction with velocity map ion imaging. The photoexcited molecules eventual I atom products are probed by site-selective at the 4d edge intense XUV pulses, which induce multiple charges initially localized to iodine atom. At separations below critical distance for charge transfer (CT), can redistribute around molecule...
By using high-resolution photoelectron velocity map imaging and a pump–probe ionization scheme we are able to demonstrate that angular distributions from ammonia depend sensitively on the neutral rotational level is ionized, of ion formed. We use this sensitivity fully determine photoionization dynamics giving rise observed branching ratios. In addition, observe dependence initially prepared alignment, by varying relative polarizations pump probe. This can be used corroborate determined...
_Additional notes:_ Authors: - Paul Hockett, National Research Council of Canada, 100 Sussex Drive, Ottawa, K1A 0R6, Canada Tim Ingleby, Department Architecture and Built Environment, Northumbria University, Ellison Place, Newcastle upon Tyne, NE1 8ST, UK Links: Online version: Authorea, DOI: 10.22541/au.148821660.05483993 Repository for videos files, Figshare, 10.6084/m9.figshare.c.3470907 Arxiv version (1610.04281) Ongoing work: femtolab.ca
The Pixel-Imaging Mass Spectrometry (PImMS) camera allows for 3D charged particle imaging measurements, in which the time-of-flight is recorded along with (x, y) position. Coupling PImMS to an ultrafast pump-probe velocity-map spectroscopy apparatus therefore provides a route time-resolved multi-mass ion imaging, both high count rates and large dynamic range, thus allowing rapid measurements of complex photofragmentation dynamics. Furthermore, use vacuum ultraviolet wavelengths probe pulse...
Quantum photonics offers much promise for the development of new technologies. The ability to control interaction light and matter at level single quantum excitations is a prerequisite construction potentially powerful devices. Here we use rotational levels room temperature ensemble hydrogen molecules couple two distinct optical modes photon using femtosecond pulses with 2 THz bandwidth. We observe correlations that violate Cauchy-Schwarz inequality, thereby verifying creation nonclassical...