13 research outputs found
Engineering an all-optical route to ultracold molecules in their vibronic ground state
We propose an improved photoassociation scheme to produce ultracold molecules
in their vibronic ground state for the generic case where non-adiabatic effects
facilitating transfer to deeply bound levels are absent. Formation of molecules
is achieved by short laser pulses in a Raman-like pump-dump process where an
additional near-infrared laser field couples the excited state to an auxiliary
state. The coupling due to the additional field effectively changes the shape
of the excited state potential and allows for efficient population transfer to
low-lying vibrational levels of the electronic ground state. Repetition of many
pump-dump sequences together with collisional relaxation allows for
accumulation of molecules in v=0.Comment: Phys. Rev. A, in pres
A systematic construction of Gaussian basis sets for the description of laser field ionization and high-harmonic generation
A precise understanding of mechanisms governing the dynamics of electrons in
atoms and molecules subjected to intense laser fields has a key importance for
the description of attosecond processes such as the high-harmonic generation
and ionization. From the theoretical point of view this is still a challenging
task, as new approaches to solve the time-dependent Schr\"odinger equation with
both good accuracy and efficiency are still emerging. Until recently, the
purely numerical methods of real-time propagation of the wavefunction using
finite grids have been frequently and successfully used to capture the electron
dynamics in small, one or two-electron systems. However, as the main focus of
attoscience shifts towards many-electron systems, such techniques are no longer
effective and need to be replaced by more approximate, but computationally
efficient ones. In this paper we explore the increasingly popular method of
expanding the wavefunction of the examined system into a linear combination of
atomic orbitals, and present a novel systematic scheme for constructing an
optimal Gaussian basis set suitable for the description of excited and
continuum atomic or molecular states. We analyze the performance of the
proposed basis sets by carrying out a series of time-dependent configuration
interaction calculations for the hydrogen atom in fields of intensity varying
from 5x10^13 W/cm2 to 5x10^14 W/cm2 . We also compare the results with data
obtained using Gaussian basis sets proposed previously by other authors.Comment: Minor changes in Sec. 1, 2 and
Global potential energy surface for the O2 + N2 interaction. Applications to the collisional, spectroscopic, and thermodynamic properties of the complex
A detailed characterization of the interaction between the most abundant
molecules in air is important for the understanding of a variety of phenomena
in atmospherical science. A completely {\em ab initio} global potential energy
surface (PES) for the O + N interaction is
reported for the first time. It has been obtained with the symmetry-adapted
perturbation theory utilizing a density functional description of monomers
[SAPT(DFT)] extended to treat the interaction involving high-spin open-shell
complexes. The computed interaction energies of the complex are in a good
agreement with those obtained by using the spin-restricted coupled cluster
methodology with singles, doubles and noniterative triple excitations
[RCCSD(T)]. A spherical harmonics expansion containing a large number of terms
due to the anisotropy of the interaction has been built from the {\em ab
initio} data. The radial coefficients of the expansion are matched in the long
range with the analytical functions based on the recent {\em ab initio}
calculations of the electric properties of the monomers [M. Bartolomei et al.,
J. Comp. Chem., {\bf 32}, 279 (2011)]. The PES is tested against the second
virial coefficient data and the integral cross sections measured with
rotationally hot effusive beams, leading in both cases to a very good
agreement. The first bound states of the complex have been computed and
relevant spectroscopic features of the interacting complex are reported. A
comparison with a previous experimentally derived PES is also provided
Different Approaches to Oxygen Functionalization of Multi-Walled Carbon Nanotubes and Their Effect on Mechanical and Thermal Properties of Polyamide 12 Based Composites
In this work the preparation of polyamide 12 (PA12) based composites reinforced with pristine and surface-modified carbon nanotubes is reported. A qualitative and quantitative evaluation of multi-walled carbon nanotube functionalization with oxygen containing reactive groups achieved by different procedures of chemical treatment is presented. Simple strong oxidative acid treatment as well as chlorination with subsequent chloroacetic acid treatment were applied. Carbon nanotubes (CNTs) were also subjected to chlorine and ammonia in gaseous atmosphere with small differences in after-ammonia treatment. Commercial COOH-functionalized carbon nanotubes were compared with nanotubes that were laboratory modified. The effect of CNT functionalization was evaluated basing on the improvement of mechanical and thermal properties of polyamide 12 composites prepared by in situ polymerization. It was found that high concentration of oxygen-containing functional groups on nanotube surface is not sufficient to improve the composite performance if the structure of carbon nanotubes is defective. Indeed, the best effects were achieved for composites containing nanotubes modified under mild conditions, seemingly due to a compromise between morphology and surface chemical structure
Chlorination of Carbon Nanotubes Obtained on the Different Metal Catalysts
In this paper, a chlorination method is proposed for simultaneous purification and functionalization of carbon nanotubes, thus increasing their ability to use. Carbon nanotubes were obtained by CVD method through ethylene decomposition on the nanocrystalline iron or cobalt or bimetallic iron-cobalt catalysts. The effects of temperature (50, 250, and 450°C) in the case of carbon nanotubes obtained on the Fe-Co catalyst and type of catalyst (Fe, Co, Fe/Co) on the effectiveness of the treatment and functionalization were tested. The phase composition of the samples was determined using the X-ray diffraction method. The quantitative analysis of metal impurity content was validated by means of the thermogravimetric analysis. Using X-ray Photoelectron Spectroscopy (XPS), Energy Dispersive Spectroscopy (EDS) analysis, and also Mohr titration method, the presence of chlorine species on the surface of chlorinated samples was confirmed
Experimental and Computational Insights into Carbon Dioxide Fixation by RZnOH Species
International audienc
Symphony on strong field approximation
This paper has been prepared by the Symphony collaboration (University of Warsaw, Uniwersytet Jagielloński, DESY/CNR and ICFO) on the occasion of the 25th anniversary of the 'simple man's models' which underlie most of the phenomena that occur when intense ultrashort laser pulses interact with matter. The phenomena in question include high-harmonic generation (HHG), above-threshold ionization (ATI), and non-sequential multielectron ionization (NSMI). 'Simple man's models' provide both an intuitive basis for understanding the numerical solutions of the time-dependent Schrödinger equation and the motivation for the powerful analytic approximations generally known as the strong field approximation (SFA). In this paper we first review the SFA in the form developed by us in the last 25 years. In this approach the SFA is a method to solve the TDSE, in which the non-perturbative interactions are described by including continuum–continuum interactions in a systematic perturbation-like theory. In this review we focus on recent applications of the SFA to HHG, ATI and NSMI from multi-electron atoms and from multi-atom molecules. The main novel part of the presented theory concerns generalizations of the SFA to: (i) time-dependent treatment of two-electron atoms, allowing for studies of an interplay between electron impact ionization and resonant excitation with subsequent ionization; (ii) time-dependent treatment in the single active electron approximation of 'large' molecules and targets which are themselves undergoing dynamics during the HHG or ATI processes. In particular, we formulate the general expressions for the case of arbitrary molecules, combining input from quantum chemistry and quantum dynamics. We formulate also theory of time-dependent separable molecular potentials to model analytically the dynamics of realistic electronic wave packets for molecules in strong laser fields. We dedicate this work to the memory of Bertrand Carré, who passed away in March 2018 at the age of 60