Surface enhanced second harmonic generation from macrocycle, catenane, and rotaxane thin films: experiments and theory.
Surface enhanced second harmonic generation (SE SHG) experiments on molecular structures, macrocycles, catenanes, and rotaxanes, deposited as monolayers and multilayers by vacuum sublimation on silver, are reported. The measurements show that the molecules form ordered thin films, where the highest degree of order is observed in the case of macrocycle monolayers and the lowest in the case of rotaxane multilayers. The second harmonic generation activity is interpreted in terms of electric field induced second harmonic (EFISH) generation where the electric field is created by the substrate silver atoms. The measured second order nonlinear optical susceptibility for a rotaxane thin film is compared with that obtained by considering only EFISH contribution to SHG intensity. The electric field on the surface of a silver layer is calculated by using the Delphi4 program for structures obtained with TINKER molecular mechanics/dynamics simulations. An excellent agreement is observed between the calculated and the measured SHG susceptibilities.
Arfaoui
Imad
I
Materials Science Centre, University of Groningen, Nijenborgh 4, NL-9747 AG Groningen, The Netherlands.
Bermúdez
Verónica
V
Bottari
Giovanni
G
De Nadai
Celine
C
Jalkanen
Jukka-Pekka
JP
Kajzar
François
F
Leigh
David A
DA
Lubomska
Monika
M
Mendoza
Sandra M
SM
Niziol
Jacek
J
Rudolf
Petra
P
Zerbetto
Francesco
F