Resonance-enhanced two-photon sum-frequency generation in NiO and KNiF<Subscript>3</Subscript>

Resonance-enhanced sum-frequency generation is introduced as a novel tool for investigation of magnetically ordered compounds. A tunable laser at frequency ₁ is used to excite an intermediate electronic transition resonantly while a second laser at frequency ₂ is used to scan the nonlinear spectrum at ₁+₂. The technique is particularly useful for investigation of centrosymmetric compounds since resonance enhancement at ₁ leads to large nonlinear signals even in the case of weakly allowed nonlinear processes. The technique is demonstrated on antiferromagnetic NiO and KNiF₃ and also shown to be useful for investigation of samples with large thickness or absorption. PACS 42.65.Ky; 78.20.Ls; 42.62.FiThis revised version was published in October 2004 with a correction to the name of Takuya Satoh.     

Theoretical study of the optical manipulation of semiconductor nanoparticles under an excitonic resonance condition

We theoretically study the mechanical interaction between radiation and a semiconductor nanoparticle, based on a microscopic model of confined excitons. The exerted force is calculated by using the Maxwell stress tensor expressed in terms of the microscopic response field. The numerical demonstrations clarify the following: (1) The enhancement of the force by using electronic resonance is remarkable for a particle with a radius of less than 100 nm for semiconductor materials. (2) The spectral peak position of the exerted force is considerably sensitive to nanoscale-size changes which would be useful for highly accurate size-selective manipulation.     

Acid-catalyzed transformation of rubrene to indenonaphthacene and its paired interacting orbital (PIO) analysis

Treatment of rubrene (5,6,11,12-tetraphenylnaphthacene) with trifluoroacetic acid in dichloromethane gives 4b,9,10-triphenyl-4b,9-dihydroindeno[1,2,3-fg]naphthacene (1) as the sole isolable product. Paired interacting orbital (PIO) analysis indicates that the reaction is initiated by preferential attack of H⁺ at C(11) position of rubrene.     

Nomura algebras of nonsymmetric Hadamard models

We show that the Nomura algebra of the nonsymmetric Hadamard model coincides with the Bose–Mesner algebra of the directed Hadamard graph.     

Catalytic asymmetric alkylation of α-cyanocarboxylates and acetoacetates using a phase-transfer catalyst

The catalytic asymmetric alkylation of α-cyanocarboxylates and acetoacetates with an alkyl halide was performed under phase-transfer conditions to afford compounds which have a chiral quaternary carbon with up to 97% and 94% ee, respectively. As applications of this method, chiral 2-oxindole derivatives and a β-lactam derivative were synthesized.