Ioannis Thanopulos - Academia.edu (original) (raw)

Papers by Ioannis Thanopulos

Molecular Physics, 2001

Results are reported on coherent monochromatic multiphoton excitation in many-level systems, whic... more Results are reported on coherent monochromatic multiphoton excitation in many-level systems, which are representative for some of the basic mechanisms for atomic and molecular multiphoton processes. Numerical solutions are discussed that use the Floquet and quasiresonant approximations in the framework of the URIMIR program package. The excitation schemes include direct three-photon excitation, two-photon excitation with diagonal coupling, Göppert-Mayer-type two-photon processes, multiphoton excitation with off-resonant intermediates, and practically irreversible coherent excitation into dense spectral structures. Several interesting phenomena are observed, such as nonlinear line shifts and broadenings of multiphoton resonances of relevance for multiphoton spectroscopy and almost constant intermediate population inversions, potentially useful for laser design. The accurate numerical results are compared with approximate solutions from perturbation theory, and with simple analytical solutions from Rabi-type formulae.

Advances in Quantum Chemistry, 2010

... 2ISZ2 (t) I splitting (see Figure 3.3) the switch on of the s1 (t) pulse results in the sirnu... more ... 2ISZ2 (t) I splitting (see Figure 3.3) the switch on of the s1 (t) pulse results in the sirnultaneousexcitation of the ... We assume no detuning (δ2= 0) of the center of the strong pulse connecting the | E0〉↔| E2〉 states. ... Coherence Effects in Laser-Induced Continuum Structure I2I n arb ...

We introduce new tubular image states (TIS) that can be formed around linear conductors and diele... more We introduce new tubular image states (TIS) that can be formed around linear conductors and dielectrics, like metallic carbon nanotubes. These Rydberg-like molecular states have a very large extent and possess peculiar physical properties. We also present a two-step light-driven enantiomeric switch, which within 100 ns can turn a mixture of left and right chiral molecules into a pure enantiomeric form. Molecular switches with more quasi-stable states can be used as dynamic memories or motors.

Physical review letters, Jan 19, 2004

We present an analytic solution to the "degenerate quantum control problem," which enab... more We present an analytic solution to the "degenerate quantum control problem," which enables the transfer of any desired fraction of population between arbitrary initial and final pure wave packets, made up of nearly degenerate energy eigenstates. It consists of two two-photon adiabatic passage steps, in which the population of the initial wave packet is first transferred, via a number of nondegenerate intermediate states, to a single eigenstate and then returned to a different target superposition state. We demonstrate the approach by executing a stepwise isomerization of three Jahn-Teller states of the Al3O molecule, where a proper optical coupling can easily be established.

The Journal of Physical Chemistry C, 2011

ABSTRACT We show that photoinduced intermolecular energy transfer can be greatly enhanced in the ... more ABSTRACT We show that photoinduced intermolecular energy transfer can be greatly enhanced in the UV frequency range in proximity to plasmonic metamaterials. The rate of the resonance energy transfer for a molecular donor−acceptor system with absorption and emission transition lines in the vacuum UV near metal-coated dielectric nanospheres is calculated by a rigorous first-principle electromagnetic Green’s tensor technique. Exemplary donor−acceptor systems based on fullerenes and organic compounds are discussed. The electronic transition spectra of the donor−acceptor molecules are obtained by ab initio calculations.

The Journal of Physical Chemistry A, 2000

ABSTRACT

Reviews of Modern Physics, 2007

The merging of coherent control ͑CC͒ and adiabatic passage ͑AP͒ and the type of problems that can... more The merging of coherent control ͑CC͒ and adiabatic passage ͑AP͒ and the type of problems that can be solved using the resulting coherently controlled adiabatic passage ͑CCAP͒ method are discussed. The discussion starts with the essence of CC as the guiding of a quantum system to arrive at a given final state via a number of different quantum pathways. The guiding is done by "tailor-made" external laser fields. Selectivity in a host of physical and chemical processes is shown to be achieved by controlling the interference between such quantum pathways. The AP process is then discussed, in which a system is navigated adiabatically along a single quantum pathway, resulting in a complete population transfer between two energy eigenstates. The merging of the two techniques ͑CCAP͒ is shown to achieve both selectivity and completeness. Application of CCAP to the solution of the nondegenerate quantum control problem is first discussed and shown that it is possible to completely transfer population from an initial wave packet of arbitrary shape, composed of a set of nondegenerate energy eigenstates, to a final arbitrary wave packet, also composed of nondegenerate states. The treatment is then extended to systems with degenerate states and shown how to induce isomerization between the broken-symmetry local minima of a Jahn-Teller Al 3 O molecule. These approaches can be further generalized to situations with many initial, intermediate, and final states and applied to quantum coding and decoding problems. CCAP is then applied to cyclic population transfer ͑CPT͒, induced by coupling three states of a chiral molecule in a cyclic fashion, ͉1͘ ↔ ͉2͘ ↔ ͉3͘ ↔ ͉1͘. Interference between two adiabatic pathways in CPT allows for a complete population transfer, coupled with multichannel selectivity, by virtue of its phase sensitivity. CPT can be used to show the purification of mixtures of right-handed and left-handed chiral molecules. Finally, quantum-field coherent control is introduced, where CCAP is extended to the use of nonclassical light. This emerging field may be used to generate new types of entangled radiation-matter states.

Physical Review Letters, 2003

We present an optical "enantio-selective switch", that, in two steps, turns a ("racemic") mixture... more We present an optical "enantio-selective switch", that, in two steps, turns a ("racemic") mixture of left-handed and right-handed chiral molecules into the enantiomerically pure state of interest. The optical switch is composed of an "enantio-discriminator" and an "enantio-converter" acting in tandem. The method is robust, insensitive to decay processes, and does not require molecular preorientation. We demonstrate the method on the purification of a racemate of (transiently chiral) D2S2 molecules, performed on the nanosecond timescale.

Physical Review Letters, 2008

We show that by using laser catalysis, we can employ translationally cold (T r 1:75 K) collisions... more We show that by using laser catalysis, we can employ translationally cold (T r 1:75 K) collisions to produce ultracold (0:01 mK < T p < 1 mK) (homonuclear) molecules. We illustrate this approach by studying the laser catalysis of the 6 Li 6 Li 7 Li ! @! 6 Li 6 Li 7 Li 1 4 A 00 ! @! 6 Li 6 Li 7 Li reaction in the collinear approximation. Ultracold 6 Li 6 Li product molecules are shown to be produced at an extraordinary yield of up to 99.97%, using moderate laser intensities of I 100 kW=cm 2 ÿ 10 MW=cm 2 .

Physical Review B, 2012

ABSTRACT We show that nonlinear optical rectification (NOR) can be greatly enhanced in the proxim... more ABSTRACT We show that nonlinear optical rectification (NOR) can be greatly enhanced in the proximity of plasmonic nanostructures. The NOR enhancement in the visible frequency range near Cu-coated SiO2 nanospheres is calculated by a rigorous first-principle electromagnetic Green's tensor technique. Exemplary compounds with absorption in the visible optical spectrum based on and metalloporphyrin molecules are discussed, exhibiting enhancement factors typically larger than ten. Their spectral properties in relation to NOR are obtained by first-principle electronic structure calculations.

Physical Review A, 2011

ABSTRACT We introduce a method for the efficient computation of non-Markovian quantum dynamics fo... more ABSTRACT We introduce a method for the efficient computation of non-Markovian quantum dynamics for strong (and time-dependent) system-bath interactions. The past history of the system dynamics is incorporated by expanding the memory kernel in exponential functions thereby transforming in an exact fashion the non-Markovian integrodifferential equations into a (larger) set of “effective modes” differential equations (EMDE). We have devised a method which easily diagonalizes the EMDE, thereby allowing for the efficient construction of an adiabatic basis and the fast propagation of the EMDE in time. We have applied this method to three-dimensional photodissociation of the H2+ molecule by strong laser fields. Our calculations properly include resonance-Raman scattering via the continuum, resulting in extensive rotational and vibrational excitations. The calculated final kinetic and angular distribution of the photofragments are in overall excellent agreement with experiments, both when transform-limited pulses and when chirped pulses are used.

Physical Review A, 2005

ABSTRACT We show that entangled radiation-matter states with broken symmetries can be prepared by... more ABSTRACT We show that entangled radiation-matter states with broken symmetries can be prepared by using nonclassical light in the coherent control techniques. We demonstrate the method by realizing the entanglement in degenerate continuum electronic momentum states of opposite directionality and discrete states of opposite handedness in chiral molecules. When the material system is excited simultaneously by classical light and quantum light in a state with several semiclassical phases, the interference conditions guide the system to such entangled radiation-matter states.

Nanotechnology, 2008

We introduce a novel molecular junction based on a thiol-functionalized porphyrin derivative with... more We introduce a novel molecular junction based on a thiol-functionalized porphyrin derivative with two almost energetically degenerate equilibrium configurations. We show that each equilibrium structure defines a pathway of maximal electric charge transfer through the molecular junction and that these two conduction pathways are spatially orthogonal. We further demonstrate computationally how to switch between the two equilibrium structures of the compound by coherent light. The optical switching mechanism is presented in the relevant configuration subspace of the compound, and the corresponding potential and electric dipole surfaces are obtained by ab initio methods. The laser-induced isomerization takes place in two steps in tandem, while each step is induced by a two-photon process. The effect of metallic electrodes on the electromagnetic irradiation driving the optical switching is also investigated. Our study demonstrates the potential for using thiol-functionalized porphyrin derivatives for the development of a light-controlled nanoscale current router.

Nano Letters, 2006

We theoretically demonstrate the possibility of dynamically controlling catalysis by nanomechanic... more We theoretically demonstrate the possibility of dynamically controlling catalysis by nanomechanical means. This novel methodology is based on switching the configuration (activity) of catalysts docked on nanoscale surfaces that are reversibly deformed. We test the approach by molecular dynamics simulations of an organic chiral catalyst that is docked by van der Waals coupling on twisted carbon nanotubes. Our results show that its catalytic activity is sharply correlated with the direction and amount of the nanotube twist. We also observe a small selectivity in docking of chiral molecules on straight helical nanotubes.

Journal of the American Chemical Society, 2005

We show that phase-coherent optical techniques allow for the detection and automatic repair of mu... more We show that phase-coherent optical techniques allow for the detection and automatic repair of mutations in nucleotide pairs. We demonstrate computationally that there is a laser pulse sequence that can detect the occurrence of a mutation caused by a double proton transfer between hydrogen-bonded nucleotide pairs and automatically repair it by converting the mutated nucleotide pair to the nonmutated one. The specific system chosen for this demonstration is the hydrogen-bonded 2-pyridone‚2-hydroxypyridine dimer at typical internucleotide distances, a well-established model for tautomeric acid base pairs.

Journal of Physics B: Atomic, Molecular and Optical Physics, 2008

ABSTRACT We present a time-dependent theory of system–bath interactions resulting in a reduced se... more ABSTRACT We present a time-dependent theory of system–bath interactions resulting in a reduced set of readily solvable integro-differential equations for the exact description of the multi-level system dynamics. We apply the method to the strong-field laser-induced dynamics of bound states interacting with multiple electronic states and multiple nuclear continua, and in particular to the bichromatic control of the photodissociation of methyl iodide, CH3 + I*(2P1/2) ← CH3I → CH3 + I(2P3/2). We have computed the complete strong-field control-map 'landscapes', depicting the yield of the I(2P3/2) ground atomic state as a function of external laser parameters. Employing pulses of 50–75 fs durations and 10–100 TW cm−2 intensities, we find yields which range between ~10% and ~45%, as compared to the natural value of ~30%. These values should be contrasted with the weak-field control case where the yields vary over the much larger range of ~0–80%, though with a much lower total dissociation yield per pulse. In addition to the above, we demonstrate the validity of the Markov approximation for strong laser-mediated system–bath interactions involving 'slowly varying' continua.

Journal of Modern Optics, 2009

ABSTRACT We review recent applications of quantum control on molecular switches by optical means.... more ABSTRACT We review recent applications of quantum control on molecular switches by optical means. We discuss diverse examples, as detection and automatic switching between nucleotide base-pairs and their undesired mutants, controlled operation of multi-configurational molecular devices for quantum information storage, and switching between the two enantiomeric forms of a chiral molecule. The variety of examples discussed demonstrates the wide range of applicability and the power of optical quantum control techniques in the fast emerging field of molecular devices.

The Journal of Chemical Physics, 2003

A global analytical representation of the electric dipole hypersurface for ammonia and isotopomer... more A global analytical representation of the electric dipole hypersurface for ammonia and isotopomers is developed as a function of bond lengths and bond angles. Its simple and general form allows for the simultaneous description of all three dipole moment components using a small number of parameters. The parameter values are determined by adjustment to dipole moment values obtained from ab