Photodynamics of amino acids under UV excitation: Extraterrestrial amino acids

Abstract

The detection of amino acids in extraterrestrial environments has important implications for astrobiology and prebiotic chemistry, yet the pathways to their syntheses and their photostability under such conditions remain unclear. In this study, we employ femtosecond UV-pump visible-probe spectroscopy to investigate the ultrafast relaxation dynamics of non-aromatic amino acids in aqueous environments, representative of those found in Murchison-type meteorites and pristine Bennu samples. Using excitation wavelengths around 210 nm and probing in the visible range, two distinct decay lifetimes are identified, revealing the coexistence of internal conversion and fluorescence decay mechanisms. Internal conversion lifetimes range from 25 to 32 ps, showing efficient non-radiative relaxation processes, while fluorescence decays have a slower timescale of about 1 ns. These findings can help clarify the excited-state relaxation pathways that influence the photostability and survival of these amino acids.