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  • 1.
    Baev, Alexander
    et al.
    KTH, Superseded Departments, Biotechnology.
    Gel'mukhanov, Faris
    KTH, Superseded Departments, Biotechnology.
    Rubio-Pons, Oscar
    KTH, Superseded Departments, Biotechnology.
    Cronstrand, Peter
    KTH, Superseded Departments, Biotechnology.
    Ågren, Hans
    KTH, Superseded Departments, Biotechnology.
    Upconverted lasing based on many-photon absorption: an all dynamic description2004In: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 21, no 2, p. 384-396Article in journal (Refereed)
    Abstract [en]

    A theory is developed for the propagation through a nonlinear medium of strong pump and amplifiedspontaneous-emission pulses. The theory is based on a solution of the density matrix equations that aims at providing an adequate treatment of the nonlinear polarization of the material without addressing the Taylor expansion over the powers of intensity. The theory has been applied for modeling of three-photon absorption induced upconverted stimulated emission of organic molecules in solvents. Numerical results are presented for the organic chromophore 4-[N-(2-hydroxyethyl)-N-(methyl)amino phenyl]-4'-(6-hydroxyhexyl sulfonyl) stilbene dissolved in dimethyl sulfoxide. The results are in good agreement with available experimental results.

  • 2.
    Cronstrand, Peter
    KTH, Superseded Departments, Biotechnology.
    Quantum chemical calculations of non-linear optical absorption2004Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis represents a quantum chemical treatise ofvarious types of interactions between radiation and molecularsystems, with special emphasis on the nonlinear opticalprocesses of Multi-Photon Absorption and Excited StateAbsorption. Excitation energies, transition dipole moments,two-photon and three-photon tensor elements have beencalculated from different approaches; density functional theoryandab-initiotheory, employing different orders ofcorrelation treatment with the purpose to provide accuratevalues as well as evaluate the quality of the lower ordermethods. A combined study of the Multi-Photon Absorption andExcited State Absorption processes is motivated partly becausethey both contribute to the total optical response of a systemsubjected to intense radiation, but also because of theirconnection through so-called sum-over-states expressions. Thelatter feature is exploited in a generalized few-states model,which incorporates the polarization of the light and thedirections of the transition dipole moments constructing anexcitation channel, which thereby enables a more comprehensivecomparison of the attained transition dipole moments withexperimental data. Moreover, by decomposing a complex nonlinearresponse process such as Two-Photon Absorption into moreintuitive quantities, generalized few-states models may alsoenable a more elaborate interpretation of computed orexperimental results from which guidelines can be extracted inorder to control or optimize the property of interest. Ageneral conclusion originating from these models is that thetransition dipole moments in an excitation channel should bealigned in order to maximize the Two-Photon Absorptionprobability. The computational framework employed is responsetheory which through the response functions (linear, quadratic,cubic) offers alternative routes for evaluating the propertiesin focus; either directly and untruncated through the singleresidue of the quadratic or cubic response func- tions orthrough various schemes of truncated sum-over-statesexpressions where the key ingredients, transition dipolemoments, can be identified from the single residue of thelinear response function and double residue of the quadraticresponse function. The range of systems treated in the thesisstretches from diatomics, such as carbon monoxide and lithiumhydride, via small to large fundamental organic molecules, suchas formaldehyde, tetrazine and the trans-polyenes, to largechro- mophores, such astrans-stilbene, cumulenes, dithienothiophene,paracyclophane and organo-metallic systems, such as theplatinum(II)ethynyl compounds.

  • 3.
    Cronstrand, Peter
    et al.
    KTH.
    Christiansen, O.
    Norman, P.
    Agren, H.
    Theoretical calculations of excited state absorption2000In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 2, no 23, p. 5357-5363Article in journal (Refereed)
    Abstract [en]

    Excitation energies and transition dipole moments between excited electronic states have been calculated using various theoretical methods to investigate the ability to describe excited state absorption. Quadratic response theory is used in combination with self-consistent field, multi-configurational self-consistent field, and coupled-cluster electronic structure methods. The results of these different methods are compared. The set of molecules considered includes lithium hydride, carbon monoxide, formaldehyde, formamide, and symtetrazine. For some of the molecules results are also compared with the method of applying linear response theory to an excited state wavefunction separately optimized by means of the multi-configurational self-consistent field method.

  • 4.
    Cronstrand, Peter
    et al.
    KTH.
    Christiansen, O.
    Norman, P.
    Ågren, H.
    Ab initio modeling of excited state absorption of polyenes2001In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 3, no 13, p. 2567-2575Article in journal (Refereed)
    Abstract [en]

    Vertical excitation energies and transition dipole moments between excited electronic states have been calculated for the trans-polyenes series C 4H 6-C 12H 14 in order to study the formation of excited state absorption spectra of these species. Quadratic response theory is applied in conjunction with the self-consistent field method and a hierarchical set of coupled-cluster methods. The convergence of the excited state absorption, with respect to wavefunction and treatment of electron correlation and also the length of the oligomer unit, is studied, revealing a considerable demand on the computational effort in order to predict the excited state spectra with precision. The organization of the excited states is found to change in character along the polyene series. The inflexion point for the vertical excitation energies between the one-photon allowed 1 1B u and the two-photon 2 1A g state is predicted to occur between hexatriene and octatetraene. Good agreement with experiment is obtained for butadiene and hexatriene for which the most accurate calculations have been carried out.

  • 5.
    Cronstrand, Peter
    et al.
    KTH, Superseded Departments, Biotechnology.
    Luo, Yi
    KTH, Superseded Departments, Biotechnology.
    Norman, P.
    Ågren, Hans
    KTH, Superseded Departments, Biotechnology.
    Ab initio calculations of three-photon absorption2003In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 375, no 02-jan, p. 233-239Article in journal (Refereed)
    Abstract [en]

    We present large scale ab initio calculations of three-photon absorption of a series of dithienothiophene based charge transfer molecules using response theory within the random phase approximation. The structure-to-property relations obtained for the three-photon absorption cross-sections are discussed and compared with those for one- and two-photon absorption.

  • 6.
    Cronstrand, Peter
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Multi-photon absorption of molecules: A TRIBUTE TO JAN LINDERBERG AND POUL JORGENSEN2005In: ADVANCES IN QUANTUM CHEMISTRY, VOL 50: A TRIBUTE TO JAN LINDERBERG AND POUL JORGENSEN / [ed] abin, JR; Brandas, E, SAN DIEGO, CA: ELSEVIER ACADEMIC PRESS INC , 2005, Vol. 50, p. 1-21Conference paper (Refereed)
    Abstract [en]

    Recent applications of response theory formulations of Olsen and Jorgensen on multi-photon absorption of molecules have been briefly reviewed. The connection between the calculated microscopic and experimentally measured macroscopic properties is derived. The performance of various computational approaches ranging from Hartree-Fock and Coupled Cluster to Density Functional theory for these spectral properties is analyzed. Using analytic response theory results as reference, the validity of the commonly applied few-states models for two- and three-photon absorption of molecules have been examined. A design strategy for three-dimensional charge-transfer multi-photon absorption systems is presented.

  • 7.
    Cronstrand, Peter
    et al.
    KTH, Superseded Departments, Chemistry.
    Norman, P.
    Luo, Yi
    KTH, Superseded Departments, Biotechnology.
    Ågren, Hans
    KTH, Superseded Departments, Biotechnology.
    Few-states models for three-photon absorption2004In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 121, no 5, p. 2020-2029Article in journal (Refereed)
    Abstract [en]

    Few-states models are derived for the calculation of three-photon absorption matrix elements. Together with earlier derived few-states models for two-photon absorption, the models are evaluated against results from response theory calculations that provide the full sum-over-states values. It is demonstrated that not even for systems with charge-transfer character, where few-states models for two-photon absorption are in excellent agreement with response theory, do the models provide a quantitatively correct description for three-photon absorption. The convergence behavior, merits, and shortcomings of the models are elucidated in some detail. The role of various characteristics of the electronic structure, such as symmetry, charge transfer, and conjugation-important for the formation of a large three-photon cross section-is analyzed. As for two-photon absorption cross sections, it is essential to consider generalized few-states models also for three-photon absorption, that is, to account for dipolar directions and laser beam polarization. Despite their poor quantitative performance, it is argued that few-states models at times can be useful for interpretation purposes when applied to three-photon absorption.

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