High-resolution vibrational electron-energy-loss spectroscopy of gaseous and solid glycine

The vibrational spectra of thin solid films of glycine deposited at temperatures between 12 and 130 K, as well as gaseous glycine, have been measured by high-resolution electron-energy-loss (HREEL) spectroscopy. The spectra are dominated by hydrogen-bonded glycine dimers when the films are deposited at low temperatures. The HREEL spectra of films deposited at higher temperature (130 K) have a different habitus that can be explained on the basis of a proton transfer reaction leading to the formation of zwitterionic glycine. Gas-phase HREEL spectra show bands characteristic of the neutral monomer of glycine. The results are discussed in relation to a previous study aiming at glycine synthesis in mixed ices under the effect of low-energy electrons.