### Résumé

The diagonal and off-diagonal tensor components of the first hyperpolarizability of a series of Λ-shaped molecules are compared by means of ab initio and semiempirical molecular orbital calculations. The calculated results are rationalized using expressions derived from a simple valence-bond charge-transfer model in which one ground and two excited state are described as a combination of one valence-bond (VB) and two charge-transfer (CT) states. In addition to the CT character, the angle (2θ) between the two donor (D)/acceptor (A) branches is a key parameter to determine the relative magnitudes between the β_{xxz} and β_{zzz} components. In the VB-2CT model, β_{xxz} presents a maximum value for 2θ = 109.47°, whereas β_{xxz} and μ_{z} have the same sign. On the other hand, β_{zzz} decreases monotonically with θ, and its variations with the CT character follow a curve with two extrema like for one-dimensional D/A chromophores. The ab initio and semiempirical calculations as well as the VB-2CT model show that Λ-shaped molecules with large first hyperpolarizability and specific η = β_{xxz}/β_{zzz} can be designed in order to build phase-matchable second-harmonic generation crystals.

langue originale | Anglais |
---|---|

Pages (de - à) | 3942-3951 |

Nombre de pages | 10 |

journal | Journal of physical chemistry A |

Volume | 107 |

Numéro de publication | 19 |

Les DOIs | |

état | Publié - 15 mai 2003 |

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*Journal of physical chemistry A*, VOL. 107, Numéro 19, p. 3942-3951. https://doi.org/10.1021/jp0272567

**Large off-diagonal contribution to the second-order optical nonlinearities of Λ-shaped molecules.** / Yang, Mingli; Champagne, Benoît.

Résultats de recherche: Contribution à un journal/une revue › Article

TY - JOUR

T1 - Large off-diagonal contribution to the second-order optical nonlinearities of Λ-shaped molecules

AU - Yang, Mingli

AU - Champagne, Benoît

PY - 2003/5/15

Y1 - 2003/5/15

N2 - The diagonal and off-diagonal tensor components of the first hyperpolarizability of a series of Λ-shaped molecules are compared by means of ab initio and semiempirical molecular orbital calculations. The calculated results are rationalized using expressions derived from a simple valence-bond charge-transfer model in which one ground and two excited state are described as a combination of one valence-bond (VB) and two charge-transfer (CT) states. In addition to the CT character, the angle (2θ) between the two donor (D)/acceptor (A) branches is a key parameter to determine the relative magnitudes between the βxxz and βzzz components. In the VB-2CT model, βxxz presents a maximum value for 2θ = 109.47°, whereas βxxz and μz have the same sign. On the other hand, βzzz decreases monotonically with θ, and its variations with the CT character follow a curve with two extrema like for one-dimensional D/A chromophores. The ab initio and semiempirical calculations as well as the VB-2CT model show that Λ-shaped molecules with large first hyperpolarizability and specific η = βxxz/βzzz can be designed in order to build phase-matchable second-harmonic generation crystals.

AB - The diagonal and off-diagonal tensor components of the first hyperpolarizability of a series of Λ-shaped molecules are compared by means of ab initio and semiempirical molecular orbital calculations. The calculated results are rationalized using expressions derived from a simple valence-bond charge-transfer model in which one ground and two excited state are described as a combination of one valence-bond (VB) and two charge-transfer (CT) states. In addition to the CT character, the angle (2θ) between the two donor (D)/acceptor (A) branches is a key parameter to determine the relative magnitudes between the βxxz and βzzz components. In the VB-2CT model, βxxz presents a maximum value for 2θ = 109.47°, whereas βxxz and μz have the same sign. On the other hand, βzzz decreases monotonically with θ, and its variations with the CT character follow a curve with two extrema like for one-dimensional D/A chromophores. The ab initio and semiempirical calculations as well as the VB-2CT model show that Λ-shaped molecules with large first hyperpolarizability and specific η = βxxz/βzzz can be designed in order to build phase-matchable second-harmonic generation crystals.

UR - http://www.scopus.com/inward/record.url?scp=0038390382&partnerID=8YFLogxK

U2 - 10.1021/jp0272567

DO - 10.1021/jp0272567

M3 - Article

AN - SCOPUS:0038390382

VL - 107

SP - 3942

EP - 3951

JO - The journal of physical chemistry. A

JF - The journal of physical chemistry. A

SN - 1089-5639

IS - 19

ER -