A5057137812- Laser-Matter Interactions and Applications
- Mass Spectrometry Techniques and Applications
- Atomic and Molecular Physics
- Laser-induced spectroscopy and plasma
- Laser Design and Applications
- Advanced Chemical Physics Studies
- Laser-Plasma Interactions and Diagnostics
- Spectroscopy and Quantum Chemical Studies
- Advanced Fiber Laser Technologies
- Spectroscopy and Laser Applications
- Solar and Space Plasma Dynamics
- Nuclear physics research studies
- Gamma-ray bursts and supernovae
- Astro and Planetary Science
- Pesticide and Herbicide Environmental Studies
- Protein Interaction Studies and Fluorescence Analysis
- Quantum optics and atomic interactions
- Molecular Junctions and Nanostructures
- Porphyrin and Phthalocyanine Chemistry
- Atomic and Subatomic Physics Research
- Ion-surface interactions and analysis
- Photocathodes and Microchannel Plates
- Ionosphere and magnetosphere dynamics
- Cold Atom Physics and Bose-Einstein Condensates
- Force Microscopy Techniques and Applications
Kansas State University
2009-2024
Green Cross International
2024
Lawrence Berkeley National Laboratory
2013-2021
High-order (three-photon or more) above-threshold dissociation (ATD) of ${\mathrm{H}}_{2}^{+}$ has generally not been observed using 800 nm light. We demonstrate a strong enhancement its probability intense 7 fs laser pulses interacting with beams ${\mathrm{H}}_{2}^{+}$, ${\mathrm{HD}}^{+}$, and ${\mathrm{D}}_{2}^{+}$ ions. The mechanism invokes dynamic control the pathway. These measurements are supported by theory that additionally reveals, for first time, an unexpectedly large...
In a joint experimental and theoretical endeavor, we explore the laser-induced dissociation ionization dynamics of H${{}_{2}}^{\phantom{\rule{-0.16em}{0ex}}\phantom{\rule{-0.16em}{0ex}}+}$ beams using sub-10-fs, 800 nm laser pulses. Our theory predicts considerable control over branching ratio two-photon three-photon above-threshold (ATD) by gating pathway on few-femtosecond timescale. We are able to experimentally demonstrate this control. Moreover, our also shows importance highly excited...
In a recent Letter, Manschwetus et al. [Phys. Rev. Lett. 102, 113002 (2009)] reported evidence of electron recapture during strong-field fragmentation H${}_{2}$---explained using frustrated tunneling ionization model. Unusually, the signature this process was detection excited H${}^{*}$ atoms. We report here an extensive study in D${}_{2}$. Our measurements encompass pulse duration, intensity, ellipticity, and angular distribution dependence D${}^{*}$ formation. While we find that mechanism...
We present kinematically complete measurements of the photo-double-ionization ethylene (double CC bond) and acetylene (triple hydrocarbons just above double-ionization threshold. discuss results in terms coincident kinetic energy photoelectrons nuclear kinetic-energy release recoiling ions. have incorporated quantum chemistry calculations to interpret which electronic states dication been populated trace various subsequent fragmentation channels. suggest pathways that involve ground excited...
The $\mathrm{H}_{3}{}^{+}$ ion is the simplest polyatomic molecule and destined to play a central role in understanding such molecules intense ultrashort laser pulses. We present first measurements of field dissociation ionization $\mathrm{D}_{3}{}^{+}$ using coincidence three-dimensional momentum imaging. Our results show features that are consequence this molecule's unique equilateral triangular geometry, providing fundamentally new system for theoretical development.
We reveal surprisingly high kinetic energy release in the intense-field fragmentation of D3+ to D+ + D with 1016 W cm−2, 790 nm, 40 fs (and 7 fs) laser pulses. This feature strongly mimics behaviour channel. From experimental evidence, we conclude that origin is due frustrated tunnelling ionization, first observation this mechanism a polyatomic system. Furthermore, unravel evidence ionization dissociation, both two-body breakup D2+ and D2, three-body D.
We demonstrate the use of cold target recoil ion momentum spectroscopy to perform state-selective measurements dissociative channels following single-photon double-ionization ${\mathrm{H}}_{2}\mathrm{O}$. The two dominant dissociation observed lead two-body (${\mathrm{OH}}^{+}+{\mathrm{H}}^{+}+2{e}^{\ensuremath{-}}$) and three-body ($2{\mathrm{H}}^{+}+\mathrm{O}+2{e}^{\ensuremath{-}}$) ionic fragmentation channels. In case we observe presence an autoionization process with a...
Experiments on the triatomic hydrogen molecular ion in intense ultrashort laser pulses are important for understanding fundamentals of polyatomic dynamics and providing a benchmark theory. Here we extend our earlier measurements [Phys. Rev. Lett. 103, 103004 (2009)] to provide comprehensive picture D${}_{3}$${}^{+}$ fragmentation 7- 40-fs, 790-nm at intensities up 10${}^{16}$ W/cm${}^{2}$. Our incorporate two- three-body coincidence three-dimensional momentum imaging involving crossed-beam...
Laser-induced dissociation of ${\mathrm{O}}_{2}^{+}$ is studied in the strong-field limit using two independent methods, namely a crossed laser--ion-beam coincidence 3D momentum imaging method and supersonic gas jet velocity map technique (790 395 nm, 8--40 fs, $~$10${}^{15}$ W/cm${}^{2}$). The measured kinetic energy release spectra from dissociative ionization ${\mathrm{O}}_{2}$ reveal vibrational structure which persists over wide range laser intensities. similar for produced incoherently...
We report techniques developed to utilize three-dimensional momentum information as feedback in adaptive femtosecond control of molecular dynamics. Velocity map imaging is used obtain the dissociating ions following interaction with a shaped intense ultrafast laser pulse. In order recover robust information, however, two-dimensional projection from detector must be inverted reconstruct full photofragments. These methods are typically slow or require manual inputs and therefore accomplished...
The dissociation of D${}_{3}$${}^{+}$ in intense ultrashort laser pulses is investigated using an improved coincidence three-dimensional momentum imaging method that allows clear separation all fragmentation channels and the determination kinetic energy release down to zero. Our results, 10-fs, 790-nm pulses, suggest a large peak at low associated with D${}^{+}$ + D${}_{2}$ channel D${}_{3}$${}^{+}$. most likely pathways leading two-body breakup are identified additional measurements 25-fs,...
The suppression of H(2)(+) strong-field dissociation has intrigued experimentalists and theorists since the early days laser-molecular science. We unravel a vibrational effect due to weak dipole-matrix element coupling strengths certain states, dependent on laser frequency-a form Cooper minima. This is demonstrated by our full-dimensional calculations persists for broad range conditions including both dissociation. Using crossed-beams coincidence, three-dimensional momentum-imaging...
A dramatic symmetry breaking in $K$-shell photoionization of the ${\mathrm{CF}}_{4}$ molecule which a core-hole vacancy is created one four equivalent fluorine atoms displayed molecular frame angular distribution photoelectrons. Observing photoejected electron coincidence with an ${\mathrm{F}}^{+}$ atomic ion after Auger decay shown to select dissociation path where core hole was localized almost exclusively on that atom. combination measurements and ab initio calculations photoelectron...
We have simultaneously measured the kinetic energy release and angular distributions for multiply charged fragmentation of diatomic molecular ions, ${{\text{N}}_{2}}^{+}$, ${\text{CO}}^{+}$, ${\text{NO}}^{+}$, ${{\text{O}}_{2}}^{+}$, in intense ultrashort laser pulses. Using a coincidence three-dimensional momentum imaging method we unambiguously separate all channels, including dissociation, since measure both neutral ionic products. Based on experimental results, conclude that mechanism...
Charge asymmetric dissociation into ${\mathrm{C}}^{2+}+\mathrm{O}$ following ionization of a CO${}^{+}$ molecular-ion beam with intense ultrashort (7--40-fs) laser pulses is studied using coincidence three-dimensional momentum imaging method. The data suggest that allowing the molecule enough time to stretch within pulse such it ionizes beyond curve crossings and ${\mathrm{C}}^{+}+{\mathrm{O}}^{+}$ potentials enhances otherwise hard-to-reach charge channel.
Molecular frame photoelectron angular distributions (MFPADs) are measured in electron-ion momentum imaging experiments and compared with complex Kohn variational calculations for carbon K-shell ionization of tetrafluoride (CF 4 ), ethane (C 2 H 6 ) 1,1-difluoroethylene F ).While the polarization averaged MFPADs show a tendency at low energies to be emitted directions bonds, opposite effect is seen CF4.A combination these behaviors difluoroethylene where from two carbons can distinguished...
A pertinent question in strong-field molecular physics is: what role does the permanent electric dipole moment of heteronuclear molecules play their dissociation dynamics? Recently, Kiess et al (2008 Phys. Rev. 77 053401) reported first evidence for direct two-photon an HD+ beam involving its moment, using 790 nm, 100 fs pulses. However, measurement was convoluted by fact that H+ (H) and D+ (D) fragments could not be well resolved. Using high resolution coincidence 3D momentum imaging, which...
The fragmentation pathways and dynamics of ethylene molecules after core ionization are explored using coincident measurements the Auger electron fragment ions by employing cold target recoil-ion momentum spectroscopy method. influence several factors on kinematics dissociation is studied. These include propensity rules, mechanisms, symmetry orbitals from which electrons originate, multiple scattering, conical intersections, interference, possible core-hole localization for double this...
We investigate the dependence of dissociation branching ratio ${\text{ND}}^{+}$ on intensity in strong-field regime. ${\text{ND}}^{+}$, unexplored previously using an intense laser, offers interesting, alternating sequence limits to ${\text{N}}^{+}+\text{D}$ and $\text{N}+{\text{D}}^{+}$ separated by less than photon energy at 795 nm wavelength. By exposing beam a 40 fs Ti:sapphire laser pulse measuring ion fragments coincidence with neutral fragments, we find that final channel depends...
The kinetic energy release (KER) and angular distribution for dissociation ionization of $\mathrm{N}_{2}{}^{+}$ in an intense short pulse $(7\phantom{\rule{0.3em}{0ex}}\mathrm{fs})$ laser at $790\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ was measured by employing a coincidence three-dimensional momentum imaging method that provides kinematically complete information on the dissociation. At intensity...
By virtue of the short lifetime excited states, we have performed three-dimensional (3D) momentum imaging on fragments from an electronically and vibrationally cold metastable ${\mathrm{CO}}^{2+}$ beam following irradiation by intense ultrashort laser pulses. This unique target can be described as a two-channel system, since most low-lying electronic states are not accessible dipole transitions due to their spin state. Laser excitation between ground ${X}^{3}\ensuremath{\Pi}$ $v=0$ state...
We present a method to measure the absolute detection efficiency of delay-line microchannel-plate detector using breakup diatomic molecular ions. This provides total efficiency, as well individual for each signal detector. The is based on fact that always yields two hits detector, but due finite some these events are recorded single particles while others detected in pairs. demonstrate by evaluating both timing and position signals laser-induced dissociation In addition, function has been...