Ignacio R. Sola

Bio: Ignacio R. Sola is an academic researcher from Complutense University of Madrid. The author has contributed to research in topics: Adiabatic process & Excited state. The author has an hindex of 22, co-authored 101 publications receiving 1926 citations. Previous affiliations of Ignacio R. Sola include Weizmann Institute of Science & Princeton University.

SHARC: ab Initio Molecular Dynamics with Surface Hopping in the Adiabatic Representation Including Arbitrary Couplings

Abstract: We present a semiclassical surface-hopping method which is able to treat arbitrary couplings in molecular systems including all degrees of freedom. A reformulation of the standard surface-hopping scheme in terms of a unitary transformation matrix allows for the description of interactions like spin−orbit coupling or transitions induced by laser fields. The accuracy of our method is demonstrated in two systems. The first one, consisting of two model electronic states, validates the semiclassical approach in the presence of an electric field. In the second one, the dynamics in the IBr molecule in the presence of spin−orbit coupling after laser excitation is investigated. Due to an avoided crossing that originates from spin−orbit coupling, IBr dissociates into two channels: I + Br(2P3/2) and I + Br*(2P1/2). In both systems, the obtained results are in very good agreement with those calculated from exact quantum dynamical simulations.

Femtosecond Intersystem Crossing in the DNA Nucleobase Cytosine.

Abstract: Ab initio molecular dynamics including nonadiabatic and spin–orbit couplings on equal footing is used to unravel the deactivation of cytosine after UV light absorption. Intersystem crossing (ISC) is found to compete directly with internal conversion in tens of femtoseconds, thus making cytosine the organic compound with the fastest triplet population calculated so far. It is found that close degeneracy between singlet and triplet states can more than compensate for very small spin–orbit couplings, leading to efficient ISC. The femtosecond nature of the ISC process highlights its importance in photochemistry and challenges the conventional view that large singlet–triplet couplings are required for an efficient population flow into triplet states. These findings are important to understand DNA photostability and the photochemistry and dynamics of organic molecules in general.

Control of ultrafast molecular photodissociation by laser-field-induced potentials

Abstract: Shaping potential energy surfaces by tailored strong laser pulses has now been shown to be a powerful method for controlling product yields in an ultrafast polyatomic photodissociation reaction. Control over the velocity of the product fragments is also achieved through the generation of light-induced conical intersections and modulating the potentials around them.

Optimal pulse sequences for population transfer in multilevel systems

Abstract: We study different mechanisms of adiabatic population transfer in N-level systems by means of optimal control algorithms. Using two-dimensional topographic maps of the yield of population transfer as a function of time delay and intensity of the pulses we analyze the global properties of the schemes and the conditions that lead to optimization. For three-level systems it is shown that the optimal pulse sequence is the well-known STIRAP (stimulated Raman adiabatic passage) scheme. For five-level systems a family of solutions ranging from the alternating STIRAP scheme to the new straddling STIRAP (S-STIRAP) scheme is obtained and the behavior of the solutions is compared. For four-level systems we obtain as optimal a S-STIRAP type sequence that behaves as an effective two-level system. For both odd and even numbers of N-level systems, the crucial role of the straddling pulse in reducing the population of all intermediate levels is demonstrated.

Selective excitation of vibrational states by shaping of light-induced potentials

Abstract: In this Letter we describe a method for population transfer using intense, ultrafast laser pulses. The selectivity is accomplished by careful shaping of light-induced potentials (LIPs). Creation and control of the LIPs is accomplished by choosing pairs of pulses with proper frequency detunings and time delays. As an example, selective population transfer is demonstrated for a three-state model of the sodium dimer.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Attosecond Physics

Abstract: Summary form only given. Fundamental processes in atoms, molecules, as well as condensed matter are triggered or mediated by the motion of electrons inside or between atoms. Electronic dynamics on atomic length scales tends to unfold within tens to thousands of attoseconds (1 attosecond [as] = 10-18 s). Recent breakthroughs in laser science are now opening the door to watching and controlling these hitherto inaccessible microscopic dynamics. The key to accessing the attosecond time domain is the control of the electric field of (visible) light, which varies its strength and direction within less than a femtosecond (1 femtosecond = 1000 attoseconds). Atoms exposed to a few oscillations cycles of intense laser light are able to emit a single extreme ultraviolet (XUV) burst lasting less than one femtosecond. Full control of the evolution of the electromagnetic field in laser pulses comprising a few wave cycles have recently allowed the reproducible generation and measurement of isolated sub-femtosecond XUV pulses, demonstrating the control of microscopic processes (electron motion and photon emission) on an attosecond time scale. These tools have enabled us to visualize the oscillating electric field of visible light with an attosecond "oscilloscope", to control single-electron and probe multi-electron dynamics in atoms, molecules and solids. Recent experiments hold promise for the development of an attosecond X-ray source, which may pave the way towards 4D electron imaging with sub-atomic resolution in space and time.

Molcas 8: New capabilities for multiconfigurational quantum chemical calculations across the periodic table.

Abstract: In this report, we summarize and describe the recent unique updates and additions to the Molcas quantum chemistry program suite as contained in release version 8. These updates include natural and spin orbitals for studies of magnetic properties, local and linear scaling methods for the Douglas-Kroll-Hess transformation, the generalized active space concept in MCSCF methods, a combination of multiconfigurational wave functions with density functional theory in the MC-PDFT method, additional methods for computation of magnetic properties, methods for diabatization, analytical gradients of state average complete active space SCF in association with density fitting, methods for constrained fragment optimization, large-scale parallel multireference configuration interaction including analytic gradients via the interface to the Columbus package, and approximations of the CASPT2 method to be used for computations of large systems. In addition, the report includes the description of a computational machinery for nonlinear optical spectroscopy through an interface to the QM/MM package Cobramm. Further, a module to run molecular dynamics simulations is added, two surface hopping algorithms are included to enable nonadiabatic calculations, and the DQ method for diabatization is added. Finally, we report on the subject of improvements with respects to alternative file options and parallelization.

Laser-induced population transfer by adiabatic passage techniques.

Abstract: We review some basic techniques for laser-induced adiabatic population transfer between discrete quantum states in atoms and molecules.