Orientador: Daniel Pereira / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-08T18:30:13Z (GMT). No. of bitstreams: 1 Costa_LeversonFariasLamonier_D.pdf: 15914858 bytes, checksum: 1c9b9d5747ffb493f5451d81d2898051 (MD5) Previous issue date: 2007 / Resumo: Neste trabalho realizamos três importantes etapas: 1) montar e caracterizar um laser selado de 13C02, 2) empregar o laser selado de 13C02 como fonte de bombeamento óptico para a molécula de metanol CH30H, e utilizá-lo pela primeira vez, para excitar o isótopo de metanol 13CH30H para geração de ondas na região do TeraHertz (THz) e 3) Propor "assignments" para as transições THz do CH30H e do 13CH30H. Para excitar as respectivas moléculas de metanol, um tubo comercial selado de 13C02 foi montado e caracterizado num ressonador laser Fabry-Perot. Dois cabeçotes de aluminio foram conectados por 4 barras de invar, separado em 135cm. Em um dos cabeçotes, temos uma grade de difração (150 linhas/mm) na configuração Littrow para selecionar as linhas de emissao do respectivo laser. 0 2° cabeçote suporta um espelho de saída de ZnSe (90% de refletividade com 10m de raio de curvatura) acoplado num PZT para sintonia fina da frequência do laser. No sistema de alimentação, usamos uma fonte de alta tensão comercial (25kV, 8mA) operando em regime DC. Com isso, utilizamos o respectivo laser para excitar as moléculas CH30H e 13CH30H, onde fomos pioneiro no uso do mesmo para bombeio óptico da molécula 13CH30H. Decorrente disso, obtemos os espectros de absorção em torno de cada linha de emissão do 13C02 dos respectivos metanol. Estes dados serviram de referenda para investigação sistemática de novas emissões THz, onde observamos e caracterizamos 12 novas linhas THz do CH30H e 19 do 13CH30H. Todas foram caracterizadas em relação ao seu comprimento de onda, offset, pressao de trabalho, polaridade e intensidade relativa.Utilizando os dados de linhas THz observados por nós, e os espectros de absorção a Transformada de Fourier do CH30H e do 13CH30H, um programa computacional intitulado "Ritz", identificou "assignments" para 4 transições THz do CH30H e 9 emissoes THz para 13CH30H, respectivamente / Abstract: In this work we accomplish three important tasks: to mount and to characterize a laser sealed-off 13C02 to optically pump first time methanol molecules CH30H and 13CH30H for generation of TeraHertz waves; Proposed assignments for transistions THz of the CH30H and 13CH30H. For optical pumping we use a commercial sealed-off 13C02, tube in a homemade Fabry-Perot laser resonator, mounted on two aluminum blocks connected by invar rods and separeted by 1.35m. One block holds a grating (150grooves/mm) used in Littrow configuration to select the emission line, while the second block supports a ZnSe output mirror (90% reflectivity and 10m radius of curvature) mounted on a PZT for fine frequency tuning. We use high voltage power supply (25kV, 8mA) to operate the 13C02 laser in CW regime. A cooling system maintains operation of the laser tube at -10o C. Output powers of l0 W and 1l0 MHz tuning range are typical for lines with higher optical gains. After, molecules CH30H and 13CH30H, optoacoustics spectroscopy (OA) signal, obtained around each sealed-off 13C02 laser line were the starting point to search for THz laser lines. For the more intense OA signal, a systematic investigation was performed to observe and characterize 12 new THz lines of the CH30H and 19 THz emissions of 13CH30H that they had been characterized in wavelength, offset, working pressure, relativepolarity and relative intensity. The available data has been compared a Ritz analysis of the high-resolution Fourier-Transform absorption spectrum of CH30H and 13CH30H, resulting in the assignments for 4 THz transistions of the CH30H and 9 THz emissions for 13CH30H, respectively / Doutorado / Física Atômica e Molecular / Doutor em Ciências

Extensive theoretical studies on the ground and excited state properties of systems containing heavy atoms have shown that accurate prediction of transition energies and related properties requires the incorporation of both relativistic and higher order correlation and relaxation effects as these effects are strongly inter- wined. The relativistic and dynamical electron correlation effects can be incor- porated in many-electron systems through a variety of many-body methods like configuration interaction (CI), coupled cluster method (CCM) etc. which are very powerful and effective tool for high precision description of electron correlation in many-electron systems. In this thesis, we investigate the relativistic and correlation effects in heavy atomic and molecular systems using these two highly correlated many-body methods. It is well recognized that, heavy polar diatomic molecules such as BaF, YbF, TlF, PbO, etc. are the leading experimental candidates for the search of violation of Parity (P ) and Time-reversal (T ) symmetry. The experimental detection of such P,T-odd effects in atoms and molecules has important consequences for the theory of fundamental interactions or for physics beyond the standard model (SM). For instance, a series of experiments on TlF have already been reported which provide the tightest limit available on the tensor coupling constant C , proton electric dipole moment (EDM) dp , etc. Experiments on YbF and BaF molecules are also of fundamental significance to the study of symmetry violation in nature, as these experiments have the potential to detect effects due to the electron EDMde. It is therefore imperative that high precession calculations are necessary to interpret these ongoing (and perhaps forthcoming) experimental outcome. For example, the knowledge of the effective electric field E(characterized by Wd) at the unpaired electron is required to link the experimentally determined P,T-odd frequency shift with the electron EDM de. We begin with a brief review of P,T-odd effects in heavy atoms and polar diatomics and the possible mechanisms which can give rise to such effects, in particular, the one arises due to the intrinsic electron EDM de. The P,T-odd interaction constant Wd is computed for the ground (2∑ ) state of YbF and BaF molecules using all-electron DF orbitals at the restricted active space (RAS) CI level. The RASCI space used for both systems in this calculation is sufficiently large to incorporate important core-core, core-valence, and valence-valence electron correlation effects. In addition to Wd, we also report the dipole moment (µe ) for these systems to assess the reliability of the method. The basis set dependency of Wd is also analyzed. The single reference coupled cluster (SRCC) method, developed by the cluster expansion of a single determinant reference function, is one of the most sophisticated method for treating dynamical correlation effects in a size-extensive manner. The non-uniqueness of the exponential nature of the wave operator diversifies the methods in multi-reference context. The multi-reference coupled cluster (MRCC) strategies fall within two broad classes: (a) State-Universal (SU), a Hilbert-space approach and (b) Valence-Universal (VU), a Fock-space approach. In this thesis, we shall be mainly concerned with the VU-MRCC which unlike SU-MRCC uses a single wave operator that not only correlates the reference functions, but also all the lower valence (or the so called subdued) sectors, obtained by deleting the occupancies systematically. The linear response theory (LRT) or equation of motion (EOM) method is another possible alternative which is nowadays extensively used to compute the atomic and molecular properties. Although, the CCLRT or EOM-CC method is not fully extensive in nature, this method has some distinct advantages over the traditional VU-MRCC theory. Further, for one-valence problem like ionization processes, the CCLRT/EOM-CC is formally equivalent to VU-MRCC, and hence, size-extensive. In this thesis, the core-extensive CCLRT and core-valence extensive (all electron) VU-MRCC methods are applied to compute the ground and excited state properties of various atomic and molecular systems (HCl, CuH, Ag, Sr, Yb and Hg) using nonrelativistic and relativistic (for heavy atoms) spinors. The similarities and differences in the structure of these two formalisms are also addressed. We also investigate the ground and excited state properties of HCN which is a system of astrophysical importance. This system has raised interest among the astrophysicists due to its detection in the atmosphere of Titan and Carbon stars. HCN has also been identified via radio-techniques in both comets and interstellar atmosphere. In the ash-photolysis of oxazole, iso-oxazole, and thiozole a transient band system was observed in the region 2500-3050 Å. This band system was attributed to a meta-stable form of HCN, i.e, either HNC or triplet HCN. We carry out detailed theoretical investigations using CCLRT and complete active space self-consistent field (CASSCF) method to characterize this unidentified band and other experimentally observed transitions.

Ce mémoire s’inscrit dans le cadre des recherches sur les molécules ultra-froides, en forte expansion depuis plusieurs années. Contrairement aux atomes, les molécules ne peuvent que très difficilement être refroidies par laser. Il est donc nécessaire d’explorer des méthodes alternatives pour parvenir à la création de gaz moléculaires ultra-froids. Ce travail théorique s’est focalisé sur une classe particulière de molécules diatomiques hétéronucléaires, présentant un moment dipolaire électrique ou magnétique intrinsèque à l’origine de leurs interactions mutuelles anisotropes.Sur la base de la connaissance précise de la spectroscopie des molécules KRb et KCs (présentant un moment dipolaire électrique intrinsèque notable), combinée à des résultats théoriques, nous avons modélisé le refroidissement de leurs degrés de liberté internes au moyen du passage adiabatique Raman stimulé (STIRAP), processus laser conduisant les molécules dans leur état fondamental absolu. Plusieurs schémas STIRAP ont été discutés et comparés entre eux du point de vue de leur efficacité.Nous avons ensuite étudié la molécule RbCa, dont la spectroscopie est encore inconnue. Cette espèce est caractérisée par la présence conjointe d’un moment dipolaire électrique et magnétique permanent, qui présente un fort intérêt pour les possibilités de contrôle des interactions anisotropes qu’ils engendrent. Nous avons déterminé la structure électronique de RbCa par deux méthodes différentes de chimie quantique, permettant ainsi de qualifier la précision des résultats. Nous avons aussi proposé un schéma de transitions laser conduisant à la formation de molécules froides de RbCa à partir des atomes séparés.La manipulation et le piégeage de molécules repose sur la connaissance de leur réponse à un champ électromagnétique externe, caractérisée par leur polarisabilité dipolaire dynamique. Les calculs de chimie quantique entrepris plus haut nous ayant permis d’accéder à des états moléculaires très excités, nous avons déterminé cette quantité pour toute une série de molécules diatomiques (dimères alcalins, RbCa, RbSr,…). Nous avons ainsi pu déterminer les paramètres optimaux pour le piégeage laser de ces molécules. / This thesis deals with ultracold molecules research, which interest has been growing for several years. Unlike atoms, laser-cooling molecules is very difficult. Alternative methods are necessary to be searched for in order to create ultracold molecular gases. This theoretical work focuses on a particular type of heteronuclear diatomic molecules, possessing an intrinsic electric or magnetic dipole moment, from which originates their mutual anisotropic interactions.Based on the precise knowledge of KRb and KCs molecules (possessing a significant intrinsic electric dipole moment) spectroscopy, combined with theoretical results, the cooling of their internal degrees of freedom using Stimulated Raman Adiabatic Passage (STIRAP), a laser process bringing molecules towards their absolute ground state, has been modelled. Several STIRAP schemes have been investigated and compared regarding their efficiency. The RbCa molecule has then been studied, which spectroscopy is still unknown. The ability of controlling the anisotropic interactions induced by the simultaneous presence of an electric and magnetic dipole moment provided by this species is a clear advantage. The electronic structure of RbCa has been computed with two methods, thus allowing to estimate the reliability of the results. A scheme of laser transitions bringing to the formation of cold RbCa molecules from separate atoms has been proposed.Manipulating and trapping molecules relies on the precise knowledge of their response to an external electromagnetic field, characterised by their dynamic dipolar polarisability. The quantum chemistry calculations mentioned earlier allowed us to compute high-lying excited states, dynamic polarisability has then been computed for a whole set of diatomic molecules (alkali dimers, RbCa, RbSr, …). The optimal parameters for trapping those molecules has then been determined.