A model exact calculation of SHG coefficients in polysubstituted push—pull polyenes

✍ Scribed by I.D.L. Albert; Puspendu K. Das; S. Ramasesha

• Publisher: Elsevier Science
• Year: 1990
• Tongue: English
• Weight: 565 KB
• Volume: 168
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(90)85143-z

✦ Synopsis

We report the model exact second-harmonic generation cceffrcients (p") in polysubstituted all-trans push-pull polyenes up to ten carbon atoms. The Pariser-Parr-Pople (PPP ) model with standard molecular parameters has been used in the calculations.

The two-state charge-transfer model in these systems is inadequate and an exact calculation is necessary to obtain reliable SHG coefficients. We find that for a fixed geometry, jI is enhanced if all the electron withdrawing substituents (pull) are successively placed from one end of the polyene chain and all the electron pushing groups (push) from the other. A twisted conformation of the polyene backbone leads to large SHG coefficients at the YAG laser frequency since the system approaches two-photon resonance. For a given chain length, the SHG coefikients increase with increase in the number of the push and pull groups.