Georges Raseev

Bio: Georges Raseev is an academic researcher from California Institute of Technology. The author has an hindex of 1, co-authored 1 publications receiving 341 citations.

Studies of differential and total photoionization cross sections of molecular nitrogen

Abstract: The photoionization of molecular nitrogen has been studied using a frozen-core Hartree-Fock final-state wave function with a correlated intitial-state wave function. The final-state wave function was obtained using the iterative Schwinger variational method. The effects of initial-state correlation were studied by comparing cross sections obtained using a configuration-interaction-type initial-state wave function with those obtained using a Hartree-Fock initial-state wave function. In this paper we compare our accurate single-center expansion results with other theoretical results. We find that earlier single-center cross sections were not well converged with respect to their expansion parameters. The results of the continuum multiple-scattering method and the Stieltjes-Tchebycheff moment-theory approach are found to be in qualitative but not quantitative agreement with the present results. We also compare our computed total cross sections as well as integrated target angular distributions with experimental results for photoionization leading to the $X^{2}\ensuremath{\Sigma}_{g}^{+}$, $A^{2}\ensuremath{\Pi}_{u}$, and $B^{2}\ensuremath{\Sigma}_{u}^{+}$ states of ${\mathrm{N}}_{2}^{+}$. We find generally good agreement, which is improved by the inclusion of initial-state correlation effects, especially in the resonant photoionization channel leading to the $X^{2}\ensuremath{\Sigma}_{g}^{+}$ state of ${\mathrm{N}}_{2}^{+}$. We also report integrated detector angular distributions for these three channels.

Measurement and laser control of attosecond charge migration in ionized iodoacetylene

Abstract: The ultrafast motion of electrons and holes after light-matter interaction is fundamental to a broad range of chemical and biophysical processes. We advanced high-harmonic spectroscopy to resolve spatially and temporally the migration of an electron hole immediately after ionization of iodoacetylene while simultaneously demonstrating extensive control over the process. A multidimensional approach, based on the measurement and accurate theoretical description of both even and odd harmonic orders, enabled us to reconstruct both quantum amplitudes and phases of the electronic states with a resolution of ~100 attoseconds. We separately reconstructed quasi-field-free and laser-controlled charge migration as a function of the spatial orientation of the molecule and determined the shape of the hole created by ionization. Our technique opens the prospect of laser control over electronic primary processes.

Attosecond Electron Dynamics in Molecules.

Abstract: Advances in attosecond science have led to a wealth of important discoveries in atomic, molecular, and solid-state physics and are progressively directing their footsteps toward problems of chemical interest. Relevant technical achievements in the generation and application of extreme-ultraviolet subfemtosecond pulses, the introduction of experimental techniques able to follow in time the electron dynamics in quantum systems, and the development of sophisticated theoretical methods for the interpretation of the outcomes of such experiments have raised a continuous growing interest in attosecond phenomena, as demonstrated by the vast literature on the subject. In this review, after introducing the physical mechanisms at the basis of attosecond pulse generation and attosecond technology and describing the theoretical tools that complement experimental research in this field, we will concentrate on the application of attosecond methods to the investigation of ultrafast processes in molecules, with emphasis i...

Nonadiabatic quantum chemistry--past, present, and future.

Abstract: 1. Background and Definitions 481 1.1. Some History 481 1.2. Conical Intersections, Derivative Couplings and the Diabatic Representation 482 1.3. Classifying Conical Intersections: Symmetry Considerations 483 1.4. Prevalence of Conical Intersections 483 1.5. Locating and Characterizing Conical Intersections 483 2. Current State of the Art 484 2.1. Conical Intersections and Radiationless Decay 484 2.1.1. Radiationless Decay of Furan (C4H4O) 484 2.2. Diabatic States and the Representation of Adiabatic Potential Energy Surfaces and Their Couplings 485 2.2.1. H for Bound States 486 2.2.2. H for Dissociative States 486 2.2.3. Determining H 486 2.3. Nuclear Dynamics for Electronically Nonadiabatic Processes 487 2.4. Nonadiabatic Effects near Surfaces and Interfaces 487 2.4.1. Semiconductor Interfaces 487 2.4.2. Metal Surfaces 487 2.5. Effects of the Environment on Nonadiabatic Processes 488 2.6. Control of Nonadiabatic Chemical Dynamics with Lasers 489 2.6.1. Routing and the Branching Plane 489 2.6.2. Controlling Photoisomerization 489 2.6.3. Cyclohexadiene (CHD) Hexatriene (HT) Photoisomerization 490 2.6.4. Vibrationally Mediated Photodissociation of NH3 490 2.6.5. Controlling Radiationless Decay 491 2.7. Conical Intersections and Mechanism for Nonadiabatic Reactions in Photobiology 491 2.7.1. Electron-Driven Proton Transfer 491 2.7.2. Intersection Space, ReactionMechanisms, and Nonadiabatic Dynamics 491 2.8. Nonadiabatic Photoelectron Spectroscopy 491 2.8.1. General Formulation Vibronic Coupling Model 492

Dyson orbitals for ionization from the ground and electronically excited states within equation-of-motion coupled-cluster formalism: Theory, implementation, and examples

Abstract: Implementation of Dyson orbitals for coupled-cluster and equation-of-motion coupled-cluster wave functions with single and double substitutions is described and demonstrated by examples. Both ionizations from the ground and electronically excited states are considered. Dyson orbitals are necessary for calculating electronic factors of angular distributions of photoelectrons, Compton profiles, electron momentum spectra, etc, and can be interpreted as states of the leaving electron. Formally, Dyson orbitals represent the overlap between an initial N-electron wave function and the N1 electron wave function of the corresponding ionized system. For the ground state ionization, Dyson orbitals are often similar to the corresponding Hartree-Fock molecular orbitals MOs; however, for ionization from electronically excited states Dyson orbitals include contributions from several MOs and their shapes are more complex. The theory is applied to calculating the Dyson orbitals for ionization of formaldehyde from the ground and electronically excited states. Partial-wave analysis is employed to compute the probabilities to find the ejected electron in different angular momentum states using the freestanding and Coulomb wave representations of the ionized electron. Rydberg states are shown to yield higher angular momentum electrons, as compared to valence states of the same symmetry. Likewise, faster photoelectrons are most likely to have higher angular momentum. © 2007 American Institute of Physics. DOI: 10.1063/1.2805393