Hyper Rayleigh Scattering of Biomolecules : the case of Thymine and Adenine

摘要

Hyper Rayleigh Scattering (HRS) is an optical process routinely used to measure the first hyperpolarizability of molecular compounds. In order to investigate the build-up of the first hyperpolarizability of DNA, we report the investigation of the first hyperpolarizability of two of its constituents, namely the bases Thymine and Adenine at the fundamental wavelength of 800 nm. In the both cases, the weakness of the HRS signal intensities recorded requires long acquisition times and statistical analysis of the data to ensure that the sensitivity is reached. For Thymine, the absence of fluorescence is verified with the recording of the HRS line spectrum. Then, Thymine first hyperpolarizability is measured and found to be β_T=2.9×10~(-30) esu using a 10 mM concentration aqueous solution. For Adenine, the problem is complicated by the presence of fluorescence. Hence, we can only determine an upper limit for the first hyperpolarizability which is set as β_A＜ 4.2 × 10~(-30) esu.