A. M Sayler

A. M Sayler
Benedictine College · Physics and Astronomy

PhD

About

137
Publications
11,635
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2,391
Citations
Additional affiliations
May 2008 - December 2008
Kansas State University
Position
  • PostDoc Position

Publications

Publications (137)
Article
Full-text available
We implement a liquid metal ion source in a 3D coincidence momentum spectroscopy setup for studying the interaction of ionic targets with intense laser pulses. Laser intensities of up to 4 ⋅ 10¹⁶ W cm⁻² allow for the observation of up to ten-fold ionization of Au⁺-ions and double ionization of Si²⁺-ions. Further, by utilizing two-color sculpted las...
Article
Full-text available
The vibrational motion of molecules represents a fundamental example of an anharmonic oscillator. Using a prototype molecular system, HeH+, we demonstrate that appropriate laser pulses make it possible to drive the nuclear motion in the anharmonic potential of the electronic ground state, increasing its energy above the potential barrier and facili...
Article
Above-threshold ionization spectra from cesium are measured as a function of the carrier-envelope phase (CEP) using laser pulses centered at 3.1 μm wavelength. The directional asymmetry in the energy spectra of backscattered electrons oscillates three times, rather than once, as the CEP is changed from 0 to 2π. Using the improved strong-field appro...
Preprint
Full-text available
Above-threshold ionization spectra from cesium are measured as a function of the carrier-envelope phase (CEP) using laser pulses centered at 3.1 $\mu$m wavelength. The directional asymmetry in the energy spectra of backscattered electrons oscillates three times, rather than once, as the CEP is changed from $0$ to $2\pi$. Using the improved strong-f...
Article
Full-text available
We investigate the intensity- and species-dependent strong-field ionization of alkali metal atoms; sodium, potassium, rubidium and caesium; by intense, few-cycle laser pulses in the short-wave infrared (sw-IR) regime at 1800 nm. The low ionization potential, I p , of these atoms allows us to scale the interaction and study the tunneling regime at s...
Chapter
The structure and dynamics of molecules are governed by the electric forces acting between electrons and nuclei. Intense, ultrashort laser pulses offer the possibility to manipulate these forces, on the time scales relevant for the motion of a molecule's constituents. Thus, laser fields can act, not only as a mechanism to trigger molecular dynamics...
Article
The spatially dependent phase distribution of focused few-cycle pulses, i.e., the focal phase, is much more complex than the well-known Gouy phase of monochromatic beams. As the focal phase is imprinted on the carrier-envelope phase (CEP), for accurate modeling and interpretation of CEP-dependent few-cycle laser-matter interactions, both the couple...
Article
By applying recently introduced, phase-of-the-phase spectroscopy [S. Skruszewicz et al., Phys. Rev. Lett. 115, 043001 (2015)], we analyze the phase-dependent photoelectron signal from Xe ionized in intense, parallel, two-color (1800 nm and 900 nm) laser fields. With such a field configuration, tuning of the relative phase between the ionizing, ω, a...
Article
Full-text available
We present a carrier-envelope phase (CEP)-stable Yb-doped fiber laser system delivering 100 µJ few-cycle pulses at a repetition rate of 100 kHz. The CEP stability of the system when seeded by a carrier-envelope offset-locked oscillator is 360 mrad, as measured pulse-to-pulse with a stereographic above-threshold ionization (stereo-ATI) phase meter....
Article
Bond rearrangement, namely the dissociation of water ions into H2++O(q−1)+ (q=1–4) following fast ion-impact ionization, unexpectedly occurs following multiple ionization of water in spite of the presumably fast “Coulomb explosion” of the transient molecular ion. Furthermore, the branching ratio of bond rearrangement is found to be nearly equal for...
Article
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We present a three-dimensional measurement of the local focal phase in a focused broadband Gaussian laser beam and find strong deviations from the commonly assumed Gouy phase, with wide ramifications for ultrafast physics.
Preprint
Full-text available
Utilizing a benchmark measurement of laser-induced ionization of an H$_2^+$ molecular ion beam target at infrared wavelength around 2 $\mu$m, we show that the characteristic two-peak structure predicted for laser-induced enhanced ionization of H$_2^+$ and diatomic molecules in general, is a phenomenon which is confined to a small laser parameter sp...
Article
We investigate dissociative single and double ionization of HeH+ induced by intense femtosecond laser pulses. By employing a semiclassical model with nuclear trajectories moving on field-dressed surfaces and ionization events treated as stochastical jumps, we identify a strong-field mechanism wherein the molecules dynamically align along the laser...
Article
Full-text available
The laser-induced fragmentation dynamics of this most fundamental polar molecule HeH+ are measured using an ion beam of helium hydride and an isotopologue at various wavelengths and intensities. In contrast to the prevailing interpretation of strong-field fragmentation, in which stretching of the molecule results primarily from laser-induced electr...
Article
Full-text available
With the emergence of high-repetition-rate few-cycle laser pulse amplifiers aimed at investigating ultrafast dynamics in atomic, molecular, and solid-state science, the need for ever faster carrier-envelope phase (CEP) detection and control has arisen. Here we demonstrate a high-speed, continuous, every-single-shot measurement and fast feedback sch...
Preprint
Full-text available
We investigate dissociative single and double ionization of HeH+ induced by intense femtosecond laser pulses. By employing a semi-classical model with nuclear trajectories moving on field-dressed surfaces and ionization events treated as stochastical jumps, we identify a strong-field mechanism wherein the molecules dynamically align along the laser...
Article
Full-text available
We investigate the influence of chirp on carrier-envelope-phase (CEP)-dependent strong-field few-cycle laser-induced photoelectron spectra of sodium, well within the multiphoton regime. Our measurements and analytical model of this process reveal a simple chirp-dependence, which has the potential to be utilized as an online monitor of laser chirp....
Preprint
Full-text available
With the emergence of high-repetition-rate few-cycle laser pulse amplifiers, aimed at investigating ultrafast dynamics in atomic, molecular and solid state science, the need for ever faster carrier-envelope phase (CEP) detection and control has arisen. Here we demonstrate a high speed, continuous, every-single-shot measurement and fast feedback sch...
Preprint
Precise knowledge of the behaviour of the phase of light in a focused beam is fundamental to understanding and controlling laser-driven processes. More than a hundred years ago an axial phase anomaly for focused monochromatic light beams was discovered and is now commonly known as the Gouy phase. Recent theoretical work has brought into question th...
Article
Full-text available
Much of our knowledge of molecular geometry and interaction dynamics comes from indirect measurements of the molecular fragments following breakup. This technique—Coulomb-explosion imaging (CEI), i.e., determining the initial molecular configuration of a system from the momenta of the resulting fragments using knowledge of the particle interactions...
Article
Full-text available
A sophisticated setup for measuring laser-induced fragmentation of an ion beam of helium hydride and an isotopologue at various wavelengths and intensities enables us to study the dynamics of this most fundamental polar molecule. In contrast to the prevailing interpretation of strong-field fragmentation, in which stretching of the molecule results...
Article
Full-text available
In strong-field ionization processes, two-color laser fields are frequently used for controlling sub-cycle electron dynamics via the relative phase of the laser fields. Here we apply this technique to velocity map imaging spectroscopy using an unconventional orientation with the polarization of the ionizing laser field perpendicular to the detector...
Article
Full-text available
A high-precision, single-shot, and real-time carrier-envelope phase (CEP) measurement at 1.8 μm laser wavelength based on stereographic photoelectron spectroscopy is presented. A precision of the CEP measurement of 120 mrad for each and every individual laser shot for a 1 kHz pulse train with randomly varying CEP is demonstrated. Simultaneous to th...
Article
Full-text available
The spatial evolution of the electric field of focused broadband light is crucial for many emerging attosecond technologies. Here the effects of the input beam parameters on the evolution of few-cycle laser pulses in the focus are discussed. Specifically, we detail how the frequency-dependent input beam geometry, chirp and chromatic aberration can...
Article
Precise knowledge of the behaviour of the phase of light in a focused beam is fundamental to understanding and controlling laser-driven processes. More than a hundred years ago, an axial phase anomaly for focused monochromatic light beams was discovered and is now commonly known as the Gouy phase¹⁻⁴. Recent theoretical work has brought into questio...
Article
We present the single-shot carrier-envelope phase (CEP) determination of a 1 Hz, multi-terawatt (TW) laser system with a setup based on spectral broadening in a hollow-core fiber and a stereographic measurement of the energy-dependent above-threshold ionization plateau. The latter is extremely sensitive to variations in CEP. As compared to the f-2f...
Article
Full-text available
We introduce a novel method for direct and accurate measurement of refractive index dispersion based on carrier-envelope phase detection of few-cycle laser pulses, exploiting the difference between phase and group velocity in a dispersive medium. In a layout similar to an interferometer, two carrier-envelope phasemeters are capable of measuring the...
Article
We investigate sequential double ionization of helium by intense near-circularly polarized few-cycle laser pulses using a semiclassical ionization model with two independent electrons. Simulated He2+ ion momentum distributions are compared to those obtained in recent benchmark experiments [M. S. Schöffler, X. Xie, P. Wustelt, M. Möller, S. Roither,...
Article
We present measured momentum distributions on the double ionization of helium with intense, near-circularly-polarized few-cycle laser pulses with a known carrier-envelope offset phase (CEP). The capability of obtaining CEP-resolved momentum distributions enables us to observe signatures of the various combinations of laser-half-cycle two-electron e...
Article
Full-text available
The carrier-envelope phase (CEP) dependence of few-cycle above-threshold ionization (ATI) of Xe is calibrated for use as a reference measurement for determining and controlling the absolute CEP in other interactions. This is achieved by referencing the CEP-dependent ATI measurements of Xe to measurements of atomic H, which are in turn referenced to...
Article
Full-text available
We present a momentum resolved study of strong field multiple ionization of ionic targets. Using a deconvolution method we are able to reconstruct the electron momenta from the ion momentum distributions after multiple ionization up to four sequential ionization steps. This technique allows an accurate determination of the saturation intensity as w...
Article
Full-text available
The velocity map of the above-threshold ionization electron spectrum at long laser wavelength exhibits a characteristic structure normal to the laser polarization, which has the appearance of a trident or a three-pronged fork. The fork like structure vanishes for few-cycle laser pulses. It is explained in terms of the classical-electron trajectorie...
Article
Full-text available
The triatomic hydrogen molecular ion is instrumental as a benchmark towards understanding the strong-field dynamics of polyatomic molecules. Using a crossed-beams coincidence three-dimensional momentum imaging method, we demonstrate clear isotopic effects in the fragmentation of D2H+ induced by 7 fs (40 fs), 790 nm laser pulses at an intensity of 1...
Article
Full-text available
Measurements and calculations of the absolute carrier-envelope-phase (CEP) effects in the photodissociation of the simplest molecule, H_{2}^{+}, with a 4.5-fs Ti:sapphire laser pulse at intensities up to (4±2)×10^{14} W/cm^{2} are presented. Localization of the electron with respect to the two nuclei (during the dissociation process) is controlled...
Article
Full-text available
Interferometrically CEP controlled few-cycle IR pulses revealed a strong influence on both, directly ionized and rescattered electrons in xenon for pulse durations from 2 to 5 cycles.
Article
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Charge asymmetric dissociation into ${\mathrm{C}}^{2+}+\mathrm{O}$ following ionization of a CO${}^{+}$ molecular-ion beam with intense ultrashort (7\char21{}40-fs) laser pulses is studied using a coincidence three-dimensional momentum imaging method. The data suggest that allowing the molecule enough time to stretch within a laser pulse such that...
Article
Full-text available
We explore very slow laser-induced dissociation processes of molecular ion beams employing an upgraded coincidence 3D momentum imaging technique. A selection of our studies, focused on zero-photon dissociation of H2+, two-body breakup of D3+, and vibrational structure in O2+ dissociation, will be presented.
Article
Full-text available
We reveal surprisingly high kinetic energy release in the intense-field fragmentation of D3+ to D+ + D+ + D with 1016 W cm−2, 790 nm, 40 fs (and 7 fs) laser pulses. This feature strongly mimics the behaviour of the D+ + D+ + D+ channel. From the experimental evidence, we conclude that the origin of the feature is due to frustrated tunnelling ioniza...
Article
Full-text available
Experiments on the triatomic hydrogen molecular ion in intense ultrashort laser pulses are important for understanding the fundamentals of polyatomic molecular dynamics and for providing a benchmark for theory. Here we extend our earlier measurements [ Phys. Rev. Lett. 103 103004 (2009)] to provide a comprehensive picture of D3+ fragmentation in 7-...
Article
Intense few-cycle (4-8fs) laser pulses at 790 nm are now being used in a wide variety of applications, including the production of attosecond extreme-ultraviolet (XUV) pulses. Since these experiments are sensitive to the electric field of the laser light, the characterization and control of the waveform is critical for the understanding and manipul...
Article
Full-text available
The charge asymmetric dissociative ionization (CADI) of a CO^+ molecular ion beam into C^2+ + O was studied by 7 and 40 fs intense (10^14i W/cm^2) laser pulses with both linear and circular polarization. Using a three-dimensional coincidence imaging technique, we detected both charged and neutral fragments. The measured kinetic energy release and a...
Article
Full-text available
Collisions between few keV molecular ions and atoms result primarily in collision-induced dissociation (CID) and dissociative capture (DC). The CID process can be a result of vibrational excitation; however, previous experimental efforts were unable to resolve the vibrational process from the competing electronic excitation, complicating comparison...
Article
Presented are the carrier-envelope phase (CEP) and energy dependent few-cycle above-threshold ionization (ATI) spectra for Xenon, Argon, Krypton and atomic Hydrogen. This data was obtained by a phase tagging technique which is based on a novel robust, real-time, every-single-shot technique for determining the CEP via a stereographic ATI setup. The...
Article
Full-text available
Despite their broad implications for phenomena such as molecular bonding or chemical reactions, our knowledge of multi-electron dynamics is limited and their theoretical modelling remains a most difficult task. From the experimental side, it is highly desirable to study the dynamical evolution and interaction of the electrons over the relevant time...
Article
Full-text available
A precise, real-time, single-shot carrier–envelope phase (CEP) tagging technique for few-cycle pulses was developed and combined with cold-target recoil-ion momentum spectroscopy and velocity-map imaging to investigate and control CEP-dependent processes with attosecond resolution. The stability and precision of these new techniques have allowed fo...
Article
Full-text available
In a joint experimental and theoretical endeavor, we explore the laser-induced dissociation and ionization dynamics of H2 + beams using sub-10-fs, 800 nm laser pulses. Our theory predicts considerable control over the branching ratio of two-photon and three-photon above-threshold dissociation (ATD) by gating the dissociation pathway on a few-femtos...
Article
Full-text available
The relative yield of highly charged atomic ions produced by a short (4–6 fs at FWHM) intense (1014–5 × 1018 W cm−2) laser pulse was investigated by numerical solution of the rate equations. We predict oscillations of the ion yield as a function of the absolute phase. A distinctive property of this phase dependence is that it can only be observed w...
Article
Full-text available
In a recent Letter, Manschwetus et al. [ Phys. Rev. Lett. 102 113002 (2009)] reported evidence of electron recapture during strong-field fragmentation of H2—explained using a frustrated tunneling ionization model. Unusually, the signature of this process was detection of excited H* atoms. We report here an extensive study of this process in D2. Our...
Article
Full-text available
Polarization gating is used to extend a real-time, single-shot, carrier-envelope phase (CEP) measurement, based on high-energy above-threshold ionization in xenon, to the multi-cycle regime. The single-shot CEP precisions achieved are better than 175 and 350 mrad for pulse durations up to 10 fs and 12.5 fs, respectively, while only 130 μJ of pulse...
Article
Full-text available
A robust nonoptical carrier-envelope phase (CEP) locking feedback loop, which utilizes a measurement of the left–right asymmetry in the above-threshold ionization (ATI) of Xe, is implemented, resulting in a significant improvement over the standard slow-loop f-to- 2 f technique. This technique utilizes the floating average of a real-time, every-sin...
Article
Full-text available
High-speed, single-shot velocity-map imaging (VMI) is combined with carrier-envelope phase (CEP) tagging by a single-shot stereographic above-threshold ionization (ATI) phase-meter. The experimental setup provides a versatile tool for angle-resolved studies of the attosecond control of electrons in atoms, molecules, and nanostructures. Single-shot...
Conference Paper
The authors have recently proposed and implemented a technique, which utilizes a stereographic measurement of the above-threshold ionization (ATI) of Xe and fast electronics, to determine the carrier-envelope phase CEP of every pulse in a kHz pulse train individually and in real-time with a precision of 6.5°. The stereo-ATI technique is ideal for d...
Article
The dominant channel in slow (few keV) collisions between a molecular ion and a target atom is dissociative capture, e.g. H2^+ + Ar -> H + H + Ar^+. Our coincidence imaging method allows us to collect all three collision products and therefore determine the efficiency of detecting the recoil ion. Using that efficiency, we measure the probability of...
Article
Full-text available
The relative yield and momentum distributions of all multiply charged atomic ions generated by a short (30 fs) intense (1014–5×1018 W/cm2) laser pulse are investigated using a Monte Carlo simulation. We predict a substantial shift in the maximum (centroid) of the ion-momentum distribution along the laser polarization as a function of the absolute p...
Article
Full-text available
The pulse lengths of intense few-cycle (4 – 10 fs) laser pulses at 790 nm are determined in real-time using a stereographic above-threshold ionization (ATI) measurement of Xe, i.e. the same apparatus recently shown to provide a precise, real-time, every-single-shot, carrier-envelope phase measurement of ultrashort laser pulses. The pulse length is...
Article
Full-text available
Single-shot carrier-envelope-phase (CEP) tagging is combined with a reaction mircoscope (REMI) to investigate CEP-dependent processes in atoms. Excellent experimental stability and data acquisition longevity are achieved. Using this approach, we study the CEP effects for nonsequential double ionization of argon in 4-fs laser fields at 750 nm and an...
Article
Full-text available
In this Letter we demonstrate a method for real-time determination of the carrier-envelope phase of each and every single ultrashort laser pulse at kilohertz repetition rates. The technique expands upon the recent work of Wittmann and incorporates a stereographic above-threshold laser-induced ionization measurement and electronics optimized to prod...
Article
Full-text available
By virtue of the short lifetime of excited states, we have performed three-dimensional (3D) momentum imaging on the fragments from an electronically and vibrationally cold metastable CO2+ 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...
Article
Full-text available
Closed-loop control schemes incorporating feedback algorithms and shaped ultrafast laser pulses have been used to control a number of molecular processes. Using carbon monoxide as a model system, we have examined how the type of feedback signal delivered to the algorithm can influence the level of control and in some cases, help provide a better un...
Article
We present a quantitative comparison between experimental measurements and theoretical calculations for laser-induced dissociation of H2^+ in an intense ultrashort pulse. The 3D momentum distribution was measured for the dissociating fragments of an H2^+ beam that has been exposed to a 10 fs, 790 nm pulse at intensities of 10^12 and 10^13 W/cm^2. W...
Article
A single collision between an H2^+ or HeH^+ projectile (at ˜ keV/amu) and an Ar atom leads predominantly to dissociative capture (DC) and collision-induced dissociation (CID). The CID process can be driven by an electronic or vibrational excitation - the latter typically occurring in close-encounter collisions. One interesting question we focus on...
Article
Evidence of net zero-photon dissociation is elusive, since the low kinetic energy release, which is the signature of this process, can also be due to resonance enhanced multi-photon ionization (REMPI) of H2 [Posthumus et al., Phys. Rev. Lett. 101, 233004 (2008)]. To eliminate the competing REMPI process we have studied an H2^+ beam target. Explicit...
Article
Full-text available
Collisions between molecular-ion projectiles and atomic targets at energies of a few keV/amu lead predominantly to dissociative capture (DC) and collision-induced dissociation (CID). The CID process can be driven by electronic or vibrational excitation. The angular distribution of electronic CID, defined as the dissociation yield versus the angle b...
Article
Full-text available
In a recent Letter, Manschwetus et al. [Phys. Rev. Lett. 102, 113002 (2009)] reported experimental evidence for the formation of metastable H* fragments upon dissociative ionization of H2 by a strong laser field. Their finding was explained using a frustrated tunnel ionization model. Here, we present our measurements of D* formation from D2 that en...
Article
Full-text available
Target ionization in close encounters between few keV simple diatomic molecular ions and noble gas targets have been studied experimentally. Some of the projectile molecular ions fragment as a result of these violent collisions while others remain bound despite undergoing a "hard" collision. The measured momenta shed light on the mechanisms respons...
Article
Full-text available
An adaptive closed-loop feedback system is used to determine the optimal pulse shapes for manipulating the branching ratio of CO2+ following ionization by an intense laser pulse. For this target, selecting between the CO2+ and C+ + O+ final states requires control of the vibrational population distribution in the transient CO2+. The ability to both...