Publications
241 results found
Shapiro EA, Khavkine I, Spanner M, et al., 2003, Strong-field molecular alignment for quantum logic and quantum control, PHYSICAL REVIEW A, Vol: 67, ISSN: 1050-2947
We discuss an approach to quantum control based on initial adiabatic tuning of the field-free Hamiltonian by a strong laser field to optimize the system for the desired transitions induced by the control laser pulse. As an illustration, we describe single-qubit, two-qubit, and some qudit logical gates within rotational and vibrational states of a diatomic molecule. Gate operations use resonant Raman transitions, and the prior adjustment of the Hamiltonian is done by a strong nonresonant aligning field.
Olaya-Castro A, Korkusinski M, Hawrylak P, et al., 2003, Effective Bloch equations for strongly driven modulation-doped quantum wells, PHYSICAL REVIEW B, Vol: 68, ISSN: 1098-0121
We study the effects of macroscopic carrier density on intersubband transitions in a modulation-doped quantum well with two electronic subbands coupled by an intense ac electric field.We propose an ansatz wave function consistent with the Hartree-Fock approximation, and we use it to derive and analyze the effective nonlinear Bloch equations.
Markevitch AN, Smith SM, Romanov DA, et al., 2003, Nonadiabatic dynamics of polyatomic molecules and ions in strong laser fields, PHYSICAL REVIEW A, Vol: 68, ISSN: 1050-2947
Ionization and/or fragmentation of large organic molecules in strong laser fields can be quantitatively understood as a transition from adiabatic to nonadiabatic dynamics of the electronic degrees of freedom. Measurements of fragmentation patterns demonstrate regular trends as a function of the size and electronic structure of a molecule. A theoretical model is presented that agrees quantitatively with the measurements for a series of polycyclic aromatic molecules.
Haljan P, Fortier T, Hawrylak P, et al., 2003, High harmonic generation and level bifurcation in strongly driven quantum wells, LASER PHYSICS, Vol: 13, Pages: 452-456, ISSN: 1054-660X
For electron densities below a critical value, a double quantum well placed in a strong oscillating electric field produces a plateau of coherent harmonic radiation, which upconverts the driving frequency by up to two orders of magnitude. Continuous harmonic generation is made possible by energy relaxation and survives complete phase relaxation within a quarter-cycle of the driving field. Above a critical electron doping density, level bifurcation leads to abrupt changes in the wave function’s phase and to the eventual disappearance of high harmonics.
Niikura H, Legare F, Hasbani R, et al., 2002, Sub-laser-cycle electron pulses for probing molecular dynamics, NATURE, Vol: 417, Pages: 917-922, ISSN: 0028-0836
Experience shows that the ability to make measurements in any new time regime opens new areas of science. Currently, experimental probes for the attosecond time regime (10(-18)-10(-15) s) are being established. The leading approach is the generation of attosecond optical pulses by ionizing atoms with intense laser pulses. This nonlinear process leads to the production of high harmonics during collisions between electrons and the ionized atoms. The underlying mechanism implies control of energetic electrons with attosecond precision. We propose that the electrons themselves can be exploited for ultrafast measurements. We use a ’molecular clock’, based on a vibrational wave packet in H-2(+) to show that distinct bunches of electrons appear during electron-ion collisions with high current densities, and durations of about 1 femtosecond (10(-15) s). Furthermore, we use the molecular clock to study the dynamics of non-sequential double ionization.
Kalosha V, Spanner M, Herrmann J, et al., 2002, Generation of single dispersion precompensated 1-fs pulses by shaped-pulse optimized high-order stimulated Raman scattering., Phys Rev Lett, Vol: 88, Pages: 103901-103901, ISSN: 0031-9007
We propose and theoretically analyze a new approach for generating and shaping 1-fs pulses. It combines the ideas of strong-field molecular optics and optimal control to manipulate light generation in a pump-probe Raman regime. Flexible phase control over the generated spectrum of about 3 eV width is achieved by controlling the input pulses and maximizing the coherence of medium excitation by adiabatically aligning molecules in the medium with a specially shaped pump pulse. The generated pulse is optimized for an output window, precompensating for its dispersion to all orders.
Verver RJ, Wright JS, Ivanov MY, 2002, Simulation of pump-probe spectroscopy of a highly-charged diatomic molecule: Role of intermediate charged states and electronic and vibrational excitation in the multiple ionization of Cl-2 and strong-field spectroscopy of Cl-2(3+), JOURNAL OF CHEMICAL PHYSICS, Vol: 117, Pages: 6991-7001, ISSN: 0021-9606
This paper is a theoretical study of the effect of a pulsed ir laser on a neutral Cl-2 molecule, leading to the creation of highly-charged molecular ions. We also develop a new quantum-mechanical model for the ionization of diatomic molecules in the tunneling regime. We consider the effects of the pump pulse duration and also the wavelength of the probe laser on the trication Cl-2(3+) which is metastable, and consider how an experiment could be performed which would lead to the observation of its vibrational spectrum. The treatment considers nuclear wave packet dynamics which begin with vertical ionization from neutral Cl-2 to Cl-2(2+), includes dynamics arising from the intermediate charged state Cl-2(2+), and electronic excitation and dissociation from the trication Cl-2(3+). The dynamical simulations of a pump-probe experiment show modulated signals which can be Fourier-transformed to yield vibrational spectra. The quality of the modulated signal changes dramatically at an intermediate (relative to the vibrational period) pump pulse duration (at ca. 50 fs). Analysis of this effect shows how to maximize the probability of observing a simple vibrational spectrum for a highly charged diatomic created in a laser field.(C) 2002 American Institute of Physics.
Hasbani R, Ostojic B, Bunker PR, et al., 2002, Selective dissociation of the stronger bond in HCN using an optical centrifuge, JOURNAL OF CHEMICAL PHYSICS, Vol: 116, Pages: 10636-10640, ISSN: 0021-9606
Using the example of the HCN molecule, we study theoretically the possibility of selectively breaking the stronger bond in a triatomic molecule by rotationally accelerating it in an optical centrifuge using a combination of two oppositely chirped and counter-rotating strong laser fields. In our simulation the resultant field forces rotational acceleration of the HCN molecule to a point where the centrifugal force between the two heavy atoms (C and N) exceeds the strength of their (triple) bond. The effects of bending, rovibrational coupling, and the Coriolis force, which conspire to prevent the molecule from rotational dissociation into HC+N, can be efficiently counteracted by simple optimization of the frequency chirp. (C) 2002 American Institute of Physics.
Itatani J, Quere F, Yudin GL, et al., 2002, Attosecond streak camera, PHYSICAL REVIEW LETTERS, Vol: 88, ISSN: 0031-9007
An electron generated by x-ray photoionization can be deflected by a strong laser field. Its energy and angular distribution depends on the phase of the laser field at the time of ionization. This phase dependence can be used to measure the duration and chirp of single sub100-attosecond x-ray pulses.
Lezius M, Blanchet V, Ivanov MY, et al., 2002, Polyatomic molecules in strong laser fields: Nonadiabatic multielectron dynamics, JOURNAL OF CHEMICAL PHYSICS, Vol: 117, Pages: 1575-1588, ISSN: 0021-9606
We report the observation and characterization of a new nonresonant strong field ionization mechanism in polyatomic molecules: Nonadiabatic multi-electron (NME) dynamics. The strong field response of a given molecule depends on important properties such as molecular geometry and bonding, the path length of delocalized electrons and/or ionization potential as well as on basic laser pulse parameters such as wavelength and intensity. Popular quasi-static tunnelling models of strong field molecular ionization, based upon the adiabatic response of a single active electron, are demonstrated to be inadequate when electron delocalization is important. The NME ionization mechanism greatly affects molecular ionization, its fragmentation and its energetics. In addition, multi-electron effects are shown to be present even in the adiabatic long wavelength limit. (C) 2002 American Institute of Physics.
Stolow A, Lezius M, Blanchet V, et al., 2001, Polyatomic molecules in strong fields: Non-adiabatic multi-electron dynamics., ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, Vol: 221, Pages: U293-U293, ISSN: 0065-7727
Ivanov MY, 2001, From strong field molecular optics to generation of subfemtosecond pulses., ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, Vol: 221, Pages: U246-U246, ISSN: 0065-7727
Yudin GL, Ivanov MY, 2001, Correlated multiphoton double ionization of helium: The role of nonadiabatic tunneling and singlet recollision, PHYSICAL REVIEW A, Vol: 64, ISSN: 1050-2947
We study the role of singlet coupling during double ionization of Helium atoms in intense laser fields, within the framework of the recollision model. The singlet. cross sections for inelastic e(+)He(+) scattering, integrated over all excitation and ionization channels, are used. Nonadiabatic corrections during tunneling of the active electron are also included.
Yudin GL, Ivanov MY, 2001, Physics of correlated double ionization of atoms in intense laser fields: Quasistatic tunneling limit (vol A 63, art. no. 033404, 2001), PHYSICAL REVIEW A, Vol: 64, ISSN: 1050-2947
Villeneuve DM, Aseyev SA, Dietrich P, et al., 2001, Centrifugal dissociation of a molecule using the optical centrifuge, 12th International Conference on Ultrafast Phenomena, Publisher: SPRINGER-VERLAG BERLIN, Pages: 326-330, ISSN: 0172-6218
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Stolow A, Lezius M, Blanchet V, et al., 2001, Polyatomic molecules in strong fields: Non-adiabatic multi-electron dynamics., ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, Vol: 221, Pages: 398-PHYS-398-PHYS, ISSN: 0065-7727
Verver RJ, Matusek DR, Wright JS, et al., 2001, Production and study of triply charged diatomic ions with femtosecond pulses: Application to Cl-2(3+), JOURNAL OF PHYSICAL CHEMISTRY A, Vol: 105, Pages: 2435-2443, ISSN: 1089-5639
We describe the preparation of diatomic trications using intense femtosecond laser pulses, and discuss the feasibility of using femtoseond pump-probe techniques to measure the vibrational spectrum of Cl-2(3+). Initial attempts to observe the vibrational spectra of Cl-2(3+) were unsuccessful. Possible refinements to the experiment are guided by calculations of the electronic states, transition moments, and field-dressed potential curves for Cl-2(3+). Solution of the time-dependent Schrodinger equation; using these theoretical data as input allow an accurate simulation of pump-probe experiments and their time-delay signals. Optimization of the experimental parameters via the simulation suggests an improved approach to obtaining the spectra of trications, with special emphasis on the unusual aspects of these systems.
Yudin GL, Ivanov MY, 2001, Physics of correlated double ionization of atoms in intense laser fields: Quasistatic tunneling limit, PHYSICAL REVIEW A, Vol: 63, ISSN: 1050-2947
We revisit the recollision picture of correlated multiphoton double ionization of atoms in strong laser fields and develop consistent semiclassical model in the tunneling limit. We illustrate the model by applying it to helium and obtain quantitative agreement with recent experiments [B. Walker, E. Mevel, Baorui Yang, P. Breger, J. P. Chambaret, A. Antonetti, L. F. DiMauro, and P. Agostini, Phys. Rev. A 48, R894 (1993); B. Walker, B. Sheehy, L. F. DiMauro, P. Agostini, K. J. Schafer, and K. C. Kulander, Phys. Rev. Lett. 73, 1227 (1994)]. Developing the model, we address several problems of general interest, such as the reduction of intense field-assisted electron-ion collision to the field-free one and the total-cross-sections that include all inelastic channels. We describe a set of important physical effects responsible for the surprisingly high yield of doubly charged ions of noble gas atoms. All effects originate from the key role of the Coulomb potential and its interplay with the laser field. In addition to the Coulomb focusing of the oscillating trajectories onto the parent ion, other effects include transient trapping of electrons after tunneling in the vicinity of the parent ion, the creation of high-velocity electrons at all phases of the laser field, and the dominant role of collisional excitation of the parent ion followed by laser-assisted ionization.
Bhardwaj VR, Aseyev SA, Mehendale M, et al., 2001, Few cycle dynamics of multiphoton double ionization, PHYSICAL REVIEW LETTERS, Vol: 86, Pages: 3522-3525, ISSN: 0031-9007
In intense field ionization, an electron removed from the atomic core oscillates in the combined fields of the laser and the parent ion. This oscillation forces repeated revivals of its spatial correlation with the bound electrons. The total probability of double ionization depends on the number of returns and therefore on the number of optical periods in the laser pulse. We observed the yield of Ne2+ relative to Ne+ with 12 fs pulses to be clearly less compared to 50 fs pulses in qualitative agreement with our theoretical model.
Ivanov MY, 2001, From strong field molecular optics to generation of subfemtosecond pulses., ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, Vol: 221, Pages: 127-PHYS-127-PHYS, ISSN: 0065-7727
Lezius M, Blanchet V, Rayner DM, et al., 2001, Nonadiabatic multielectron dynamics in strong field molecular ionization, PHYSICAL REVIEW LETTERS, Vol: 86, Pages: 51-54, ISSN: 0031-9007
We report the observation of a general strong field ionization mechanism due to highly nonadiabatic multielectron excitation dynamics in polyatomic molecules. We observe that such excitation mechanisms greatly affect molecular ionization, fragmentation, and energetics. We characterized this phenomenon as a function of optical frequency, intensity, and molecular properties.
Spanner M, Ivanov MY, 2001, Angular trapping and rotational dissociation of a diatomic molecule in an optical centrifuge, JOURNAL OF CHEMICAL PHYSICS, Vol: 114, Pages: 3456-3464, ISSN: 0021-9606
We perform a detailed quantum study of forced molecular rotation in an optical centrifuge, recently proposed by J. Karczmarek [Phys, Rev. Lett. 82, 3420 (1999)]. The approach uses strong nonresonant laser fields with chirped frequency to induce efficient rotational excitation of anisotropic molecules via a sequence of Raman transitions. Quantum calculations firstly of angular confinement (angular trapping) of a molecule in the early stages of the centrifuge evolution and secondly of the resulting rotational dissociation process are carried out herein. The trapping calculations include both angular degrees of freedom while the dissociation calculations include one vibrational and one rotation degree of freedom. Diatomic Cl-2 is used as a test case. An extension of the scheme outlined by Karczmarek is proposed as a method of producing molecules in a single selected J = J(z) level. (C) 2001 American Institute of Physics.
Spanner M, Davitt KM, Ivanov MY, 2001, Stability of angular confinement and rotational acceleration of a diatomic molecule in an optical centrifuge, JOURNAL OF CHEMICAL PHYSICS, Vol: 115, Pages: 8403-8410, ISSN: 0021-9606
Modern femtosecond technology can be used to create laser pulses that induce controlled spinning of anisotropic molecules to very high angular momentum states (“optical centrifuge”). In this paper we extend our previous study [M. Spanner and M. Ivanov, J. Chem. Phys. 114, 3456 (2001)] and focus on the stability of angular trapping and forced rotational acceleration of a diatomic molecule in an optical centrifuge. The effects of laser intensity modulations and rovibrational coupling are analyzed in detail, classically and quantum mechanically. The numerical simulations show excellent qualitative agreement between the quantum and classical systems. Forced rotations of the classical system can exhibit chaotic behavior, which becomes rather unique when the accelerating rotation of the angular trapping potential combines with efficient rovibrational coupling. In this regime the Lyapunov exponent becomes time-dependent and the trajectories separate as exp(lambdaF(t)). (C) 2001 American Institute of Physics.
Yudin GL, Ivanov MY, 2001, Nonadiabatic tunnel ionization: Looking inside a laser cycle, PHYSICAL REVIEW A, Vol: 64, ISSN: 1050-2947
We obtain a simple closed-form analytical expression for ionization rate as a function of instantaneous laser phase phi (t), for arbitrary values of the Keldysh parameter gamma, within the usual strong-field approximation. Our analysis allows us to explicitly distinguish multiphoton and tunneling contributions to the total ionization probability. The range of intermediate gamma similar to1, which is typical for most current intense field experiments, is the regime of nonadiabatic tunneling. In this regime, the instantaneous laser phase dependence differs dramatically from both quasistatic tunneling and multiphoton limits. For cycle-averaged rates, our results reproduce standard Keldysh-Iike expressions.
Villeneuve DM, Aseyev SA, Dietrich P, et al., 2000, Forced molecular rotation in an optical centrifuge, PHYSICAL REVIEW LETTERS, Vol: 85, Pages: 542-545, ISSN: 0031-9007
Intense linearly polarized light induces a dipole force that aligns an anisotropic molecule to the direction of the field polarization. Rotating the polarization causes the molecule to rotate. Using femtosecond laser technology, we accelerate the rate of rotation from 0 to 6 THz in 50 ps, spinning chlorine molecules from near rest up to angular momentum states J similar to 420. At the highest spinning rate, the molecular bond is broken and the molecule dissociates.
Villeneuve DM, Aseyev S, Ivanov MY, et al., 2000, Molecular Optics - Using lasers to push molecules around, Proceeding of Lasers-99, Editors: Corcoran, Corcoran, Publisher: STS Press, McLean
Wright JS, DiLabio GA, Matusek DR, et al., 1999, Dissociation of molecular chlorine in a Coulomb explosion: Potential curves, bound states, and deviation from Coulombic behavior for Cl-2(n+) (n=2,3,4,6,8,10), PHYSICAL REVIEW A, Vol: 59, Pages: 4512-4521, ISSN: 1050-2947
Highly charged molecular ions are generated in Coulomb explosion experiments involving multielectron dissociative ionization, but little is known about the precise mechanisms involved in their formation. To help improve the understanding of such experiments, potential energy curves are calculated in this paper for diatomic chlorine (Cl-2) and its ions Cl-2(n+), where n=1,2,3,4,6,8,10. Bound vibrational states an obtained in three low-lying electronic states for Cl-2(2+) and one state for Cl-2(3+). Vertical excitation energies are given for stepwise excitations up to Cl-2(10+). For all the ions examined there is a significant energy defect (Delta) from the corresponding Coulomb potential, in one case reaching magnitudes of over 20 eV. We analyze the origin of these energy defects in terms of residual chemical bonding, and discuss the contribution of strongly bonding configurations at short internuclear distance; Finally, we present a simple physical model which describes the qualitative behavior of Delta(R,Q). [S1050-2947(99)01606-6].
Ivanov MY, Terent yeva LV, 1999, Steady soliton-like solutions of Euler’s equations with intrinsic force fields?, PMM JOURNAL OF APPLIED MATHEMATICS AND MECHANICS, Vol: 63, Pages: 249-256, ISSN: 0021-8928
Steady solutions of a system of Euler’s equations when there are intrinsic force interactions of electrical and gravitational type are analysed. Particular attention is devoted to the class of soliton “particle-like” solutions with concentrated charge and mass. Periodic steady solutions for the case when the intrinsic gravitational field has non-zero density at infinity is also considered. (C) 1999 Elsevier Science Ltd. All rights reserved.
Javanainen J, Ivanov MY, 1999, Splitting a trap containing a Bose-Einstein condensate: Atom number fluctuations, PHYSICAL REVIEW A, Vol: 60, Pages: 2351-2359, ISSN: 1050-2947
We theoretically study atom number fluctuations between the halves of a double-well trap containing a Bose-Einstein condensate. The basic tool is the two-mode approximation, which assumes that only two one-particle states are involved. An analytical harmonic-oscillator-like model is developed and verified numerically for both stationary fluctuations in the ground state of the system, and for the fluctuations resulting from splitting of a single trap by dynamically erecting a barrier in the middle. With increasing strength of the atom-atom interactions and/or increasing height of the potential barrier, the fluctuations tend to evolve from Poissonian to sub-Poissonian. Limits of validity of the two-mode model and its relations to the phase-atom-number approach of Leggett and Sols [A. J. Leggett and F. Sols, Found. Phys. 21, 353 (1991)] are discussed in detail. [S1050-2947(99)07809-9].
Ivanov MY, Tikhonova OV, Fedorov MV, 1998, Semiclassical dynamics of strongly driven systems, PHYSICAL REVIEW A, Vol: 58, Pages: R793-R796, ISSN: 1050-2947
A nonperturbative analytical semiclassical approach describing the interaction of a quantum system with strong oscillating fields is presented, including the limit where the external high-frequency field destroys the classical trajectories of a field-free system. Applied to ionization of a Rydberg atom, our approach allows us to describe the so-called “interference” and “adiabatic” mechanisms of laser-induced stabilization of atomic Rydberg states in a unified way. [S1050-2947(98)50208-9].
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