Controlled localization of interacting bosons in a disordered optical lattice

We show that tunneling and localization properties of interacting ultracold atoms in an optical lattice can be controlled by adiabatically turning on a fast oscillatory force even in the presence of disorder. Our calculations are based on the exact solution of the time-dependent Schroedinger equation, using the Floquet formalism. Implications of our findings for larger systems and the possibility of controlling the phase diagram of disordered-interacting bosonic systems are discussed.Comment: 7 pages 7 fig

Quantum adiabatic theorem in light of the Marzlin-Sanders inconsistency

A consensus that questions the perfunctory use of the quantum adiabatic theorem has emerged since Marzlin and Sanders [Phys. Rev. Lett. {\bf 93}, 160408 (2004)] showed the existence of an inconsistency in the applicability of the theorem. Further analysis proved that the inconsistency may arise from the existence of resonant terms in the Hamiltonian, but recent work indicates that the debate about the full extent of the problem remains open. Here, we first show that key premises required in the standard demonstration of the theorem do not hold for a dual Hamiltonian involved in the Marzlin-Sanders inconsistency. Also, we show that two simple conditions can identify systems for which the adiabatic approximation fails, in spite of satisfying traditional quantitative conditions that were believed to guarantee its validity. Finally, we prove that the inconsistency only arises for Hamiltonians that contain resonant terms whose amplitudes go asymptotically to zero.Comment: Published version. It contains some changes with respect to previous version

Irradiation of benzene molecules by ion-induced and light-induced intense fields

Benzene, with its sea of delocalized $\pi$-electrons in the valence orbitals, is identified as an example of a class of molecules that enable establishment of the correspondence between intense ion-induced and laser-light-induced fields in experiments that probe ionization dynamics in temporal regimes spanning the attosecond and picosecond ranges.Comment: 4 ps figure

Banco de dados sobre inimigos naturais de pragas que ocorrem no Brasil.

Tem-se utilizado das principais fontes de informações na área entomológica brasileira para a elaboração de um banco de dados sobre agentes biológicos de controle de pragas que ocorrem no Brasil. Já foram processadas 1680 referencias que estão disponíveis para recuperação. Nossa expectativa e atingir 2000 referencias ate meados de 1994. A base de dados esta sendo elaborada em um "software" gerenciador de bancos de dados, desenvolvido pelo CNPTIA/EMBRAPA, compatível com os sistemas operacionais UNIX e DOS. Através desta base, o usuário poderá rapidamente resgatar referencias sobre a literatura nacional que trata aspectos específicos de seu interesse. Ate o final de 1994, a primeira edição desta base estará disponível em disquetes para os interessados que atuam na área de controle biológico

Physical and spectroscopic properties of pure C2H4 and CH4:C2H4 ices

[EN] Physical and spectroscopic properties of ices of C2H4 and CH4:C2H4 mixtures with 3:1, 1:1 and 1:3 ratios have been investigated at 30 K. Two laboratories are involved in this work. In one of them, the density and refractive index of the samples have been measured by using a cryogenic quartz microbalance and laser interferometric techniques. In the other one, IR spectra have been recorded in the near- and mid-infrared regions, and band shifts with respect to the pure species, band strengths of the main bands, and the optical constants in both regions have been determined. Previous data on ethylene and the mixtures studied here were scarce. For methane, both the wavenumbers and band strengths have been found to follow a regular pattern of decrease with increasing dilution, but no pattern has been detected for ethylene vibrations. The method employed for the preparation of the samples, by vapour deposition under vacuum, is thought to be adequate to mimic the structure of astrophysical ices. Possible astrophysical implications, especially by means of the optical constants reported here, have been discussed.This work has been funded by the Ministerio de Ciencia y Competitividad (MINECO) of Spain under grants FIS2013-48087-C2-1P, FIS2013-48087-C2-2P and AYA2015-71975-REDT 'Polvo Cosmico' by the Ministerio de Ciencia e Innovacion of Spain under grant CDS2009-00038 and by the European Research Council project ERC-2013-Syg 610256 'Nanocosmos'. GM acknowledges MINECO PhD grant BES-2014-069355. Our skillful technicians C. Santonja, M. A. Moreno, A. Gonzalez and J. Rodriguez are also gratefully acknowledged.Molpeceres, G.; Satorre Aznar, MÁ.; Ortigoso, J.; Zanchet, A.; Luna Molina, R.; Millán Verdú, C.; Escribano, R.... (2017). Physical and spectroscopic properties of pure C2H4 and CH4:C2H4 ices. Monthly Notices of the Royal Astronomical Society. 466(2):1894-1902. https://doi.org/10.1093/mnras/stw3166S18941902466

TIME EVOLUTION OF PENDULAR STATES OF ASYMMETRIC-TOP MOLECULES

[1]. B. Friedrich and D.R. Herschbach, Nature 353, 412 (1991). [2]. D.T. Moore, L. Oudejans, and R.E. Miller, J. Chem. Phys., 110, 197 (1999), and refs, therein.Author Institution: Instituto de Estructura de la MateriaMolecular rotation can be transformed by the interaction with a strong electric field into a pendular motion [1] in which the molecular axis is oriented or aligned. Usually, two electrodes are used to apply a de electric field to the molecules [2]. Due to the border effects of the conducting plates the field does not zero suddenly but it extends far from the plats. Therefore, molecules traveling in a beam experience a varying electric field when they approach the Stark plates. Here, we investigate the adiabaticity of the population transfer for molecular ensembles from the field-free region to the static-field region. Rotational-eigenvalue trajectories as a function of electric field strength can present many avoided crossings for asymmetric-top molecules. These crossings will be transversed diabatically or adiabatically depending on the ratio between the variation of the field and the size of the avoided crossings. In the ideal case of every crossing being avoided. the population distribution of the ensemble in the field will be the same of the field-free molecular ensemble. We solve the time-dependent Sch\""{o}dinger equation by using a propagator based on a modified split-operator technique combined with the Riemann integral product method. The high efficiency of this method allows us the propagation of rotational wavefunctions for very long times, which is needed for going from the field-free region to the static-field region. Examples for several molecules will be presented

K-SCRAMBLING IN A NEAR-SYMMMETRIC-TOP MOLECULE CONTAINING AN EXCITED NON-COAXIAL INTERNAL ROTOR

Author Institution: Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Cientifficas; Optical Technology Division, National Institute of Standards and technologyClassical trajectories on rotational energy surfaces and coherent-state quantum projections have been used to study an asymmetric-top molecule containing a freely rotating internal symmetric top whose symmetry axis is not coincident with a principal axis of the molecule. Stationary points on the rotational energy surface, which strongly influence the trajectories, increase in number from two to four to six as $J/n$ increases from zero to infinity (where $J$ is the total and $n$ is the free-internal-rotor angular momentum). For some $J/n$ values trajectories can arise which sample a large fraction of $K$ values (where $K$ is the z-axis projection of $J$), corresponding in quantum wavefunctions to extensive $K$-mixing in the symmetric-top basis set $|J,K|$. When such mixing cannot be made small for any choice of z axis we call it $K$-Scrambling. For typical values of the torsion-rotation coupling parameter $\rho$, rotational eigenfunctions for given $J$ and torsional state turn out to be quite different from eigenfunctions for the same $J$ in some other torsional state. Nonzero rotational overlap integrals are then distributed among many rotational functions for each $(n, n^{\prime})$ pair, which may in turn contribute to internal rotation enhancement of intramolecular vibrational energy redistribution. We have also examined near-free-rotor levels of our test molecule acetaldehyde, which arise for excitation of ten or more quanta of methyl group torsion, and find that barrier effects do not change the qualitative picture obtained from the free-rotor treatment

APPLICATION OF ROTATIONAL ENERGY SURFACES TO ROTATION-TORSION EIGENFUNCTION LABELING PROBLEMS

$^{1}$ W. G. Harter and C. W. Patterson, J. Chem. Phys. 80, 4241-4261 (1988).Author Institution: Molecular Physics Division, National Institute of Standards and TechnologyThe assignment of high-J rotation-torsion or vibration-rotation-torsion transitions in acetaldehyde is complicated by labeling problems for numerical eigenvectors obtained by diagonalizing the Hamiltonian matrix. These labeling problems arise because of strong mixing of the basis functions used in the TAM (PAM-IAM hybrid) basis set, which in turn is caused by a competition between the a-principal-axis, the c-principal-axis and the methyl-top-axis for dominance in determining the axis of quantization of the projection quantum number of the total angular momentum J. Harter and $Patterson^{1}$ introduced the concept of rotational energy surfaces, and illustrated their use both classically and semi-classically for obtaining simple descriptions of high-J three-dimensional semi-rigid-body rotations in terms of J-projection quantizations along various axes in the molecule. In the present work we are trying to extend their ideas to find approximate quantization directions (and therefore approximately good projection quantum number labels) for rotational motion in acetaldehyde, which can be thought of classically as a three-dimensional rotor containing a hindered gyroscope. The details of the approach will differ for states well below the top of the barrier, near the top of the barrier, and well above the top of the barrier, since the torsional motion changes from nearly harmonic small-amplitude oscillations to nearly free internal rotation in this energy range. Since the concept of rotational energy surfaces is based on the adiabatic freezing of rotations with respect to other degrees of freedom in the molecule, we expect application of this approach to be most difficult near the top of the barrier, where the degree of change of wave functions from those of a harmonic oscillator to those of a free rotor may be quite sensitive to the J value

APPLICATION OF THE DIABATIC CORRELATION METHOD TO LABELING SPECTRA OF MOLECULES CONTAINING AN INTERNAL ROTOR

Author Institution: Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Cientificas; Optical Technology Division, National Institute of Standards and TechnologyLabeling problems for rotational energy levels of asymmetric-top molecules containing a noncoaxial internal rotor are investigated by using Rose and Kellman's diabatic correlation methods. We find that $v_{t} = 2$ and $v_{t} = 3$ rotation-torsion eigenstates for acetaldehyde, which lie just below and just above the barrier to internal rotation, can be unambiguously and meaningfully labeled by nominal quantum numbers $K_{a}$ corresponding to eigenstates of a suitably chosen zeroth-order symmetric-top Hamiltonian. Such a $K_{a}$ labeling is shown to be superior to that based on eigenvector composition for this near-prolate asymmetric rotor. The $K_{a}$ assignments from the diabatic correlation method agree with assignments made using the criterion, based on spectroscopic intuition, of smooth variation of the B value along a series of levels of given $K_{a}$ and increasing J. As a second example, the $v_{t} = 0$ state of acetamide lies near the top of the very low barrier in this near oblate top molecule. For these torsion-rotation states also, meaningful $K_{a}$ labels can be determined from the diabatic correlation method. A discussion of the method and of the results obtained for these two example molecules will be presented