The first hyperpolarizabilities of the DNA bases thymine and cytosine were determined by hyper-Rayleigh scattering in neat water despite their low solubility. Due to the low intensity levels collected, count statistics were performed instead of the standard dilution procedure. The first hyperpolarizabilities were found to be beta(Thymine) = (2.99 +/- 0.44) x 10(-30) esu for thymine and beta(Cytosine) = (3.35 +/- 0.21) x 10(-30) esu for cytosine. Due to its weak solubility, only an upper limit beta(Adenine) < (1.82 +/- 0.10) x 10(-30) esu could be set for adenine. The first hyperpolarizability of guanine could not be measured because of its very weak solubility. Theoretical static and 800 nm dynamic first hyperpolarizability tensor elements were also computed with Gaussian 09 for comparison. Published under an exclusive license by AIP Publishing.
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