Download or read book DURIP97 Instrumentation for Characterization of Two Photon Absorbing Organic Materials written by Seith Marder and published by . This book was released on 1998 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: DURIP funds were used to purchase a Spex Model FL112 High Performance Research Grade Fluorimeter and a Nd:YAG-pumped nanosecond Optical Parametric Oscillator Laser System with tunability from 440 nm - 1800 nm. This equipment was used to measure the two-photon absorption spectra for a variety of molecules from different classes and identify promising candidate molecules to meet DoD requirements for a variety of applications. A strategy for the design of molecules with large two-photon absorption cross sections has been developed. The strategy is based on the concept that symmetric charge transfer, from the ends of a conjugated system to the middle, or vice versa, upon excitation is correlated to enhanced two-photon absorption cross sections. It was shown that newly synthesized bis-styrylbenzene derivatives with donor-acceptor-donor, and acceptor-donor-acceptor structural motifs exhibit exceptionally large two-photon absorption cross sections, up to roughly 400 times that of trans-stilbene.

Download or read book DURIP 99 Instrumentation for Characterization of Two Photon and Excited State Properties of Conjugated Molecules written by and published by . This book was released on 2000 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report summarizes the status of the apparati which have been created or augmented by equipment purchased under the titled DURIP grant. Initial progress made using these systems in studies of two-photon absorption and optical limiting is also reported. Two new measurement systems have been set up and are operational. These systems are: (1) nanosecond transient absorption spectroscopy, and (2) femtosecond time resolved absorption spectroscopy. The transient spectroscopy systems provide a capability for monitoring the time evolution of transient species over the time scale of approximately equal 100 fs to milliseconds, by following absorption bands in the range of approximately equal 300 to 1000 nm. Initial results obtained using the new systems described above are presented. (1) The optical limiting properties of a new charge transfer complex (bis-(dibutylamino)stilbene:(2,4,7-trinit-9-ylidene)malononitrile; BDAS:TNFDM) are reported. This complex shows a sizeable nonlinear response at 600nm which is dependent on solvent polarity, with the strongest response in toluene solution. (2) the solvent dependence of the nonlinear transmission response of BDAS, which is dominated by two-photon induced excited state absorption (TPESA), is reported. Very large nonlinear absorption coefficients are observed in polar solvents like acetonitrile, alcohols and acetone, up to a factor of 10 larger than that in toluene. This indicates that optimization of the environment can be important for TPESA chromophores like BDAS.