Figure 1.

(a) (left). Transient absorption spectra of hydrated electron recorded 15 ps, 100 ps and 230 ps after the passage of the 7 ps electron pulse for water and solutions of 3.3 × 10⁻⁸ M naked 15 nm gold nanoparticles in water (Au_n) at 23 °C. The transient spectra at different times are scaled for clarity. Details of gold nanoparticle solutions are described in the methods section. (b) (right). Cerenkov radiation absorption spectrum for different solutions are compared. Note that the gold nanoparticle solution has more than eight orders of magnitudes smaller concentrations than the D₂SO₄ solutions.