The internal energy of sputtered glycerol molecules, determined by photoionization mass spectrometry

Abstract

The mass spectrum of thermally evaporated glycerol is measured as a function of temperature by photoionization mass spectrometry (PIMS) at two wavelengths, the Ar i (11.8 eV) and Kr i (10.6 eV) resonance lines. Also the PIMS of glycerol molecules sputtered from the liquid at 267 K is measured. By comparison with the vapor phase measurements, the internal temperature of the sputtered molecules is determined as 190±40 K. Then the assumed ejection by a ‘‘thermal spike’’ must be followed by an expansion which cools the sputtered molecules to an internal temperature which is even lower than the temperature of the liquid. Applying an analytical deconvolution, the breakdown curve of the glycerol molecules is calculated. Comparison between the Ar i and Kr i vapor phase data shows that only 0.3 eV of the excess energy of the argon photon is converted into internal energy.