Internal Energies of Ion-Sputtered Neutral Tryptophan and Thymine Molecules Determined by Vacuum Ultraviolet Photoionization

Abstract

Vacuum ultraviolet photoionization coupled to secondary neutral mass spectrometry (VUV-SNMS) of deposited tryptophan and thymine films are performed at the Chemical Dynamics Beamline. The resulting mass spectra show that while the intensity of the VUV-SNMS signal is lower than the corresponding secondary ion mass spectroscopy (SIMS) signal, the mass spectra are significantly simplified in VUV-SNMS. A detailed examination of tryptophan and thymine neutral molecules

Desorption Dynamics, Internal Energies, and Imaging of Organic Molecules from Surfaces with Laser Desorption and Vacuum Ultraviolet (VUV) Photoionization

“…Previous VUV secondary neutral mass spectrometry (VUV-SNMS) experiments have revealed that neutral biomolecules released from a surface after sputtering by 25 keV Bi 3 + ions have about 2.5 eV of internal energy. [14] Although such high-energy ion beams are well suited for high spatial resolution imaging down to 100 nm, this energy can yield significant amounts of molecular fragmentation. In this study, the energies imparted into neutral molecules desorbed by a 349 nm laser are investigated using two different methods: one by utilizing fragmentation ratios and the second by measuring the appearance energies of fragments.…”

“…It is well known that the amount of fragmentation in a mass spectrum is extremely sensitive to the amount of internal energy within the parent ion or neutral molecule. [13,14] Clearly, threshold ionization reduces the amount of fragmentation in a mass spectrum by minimizing the internal excitation of the molecules during the ionization step. [15] For large molecules (long-chain hydrocarbons or biomolecules), the internal energy imparted to the neutral molecule to introduce it into the gas phase is equally as important as the energy imparted upon photoionization.…”

“…[23][24][25][26] Very recently, the internal energy of tryptophan and thymine formed upon ion sputtering was quantified, and similar methods will be used here to ascertain internal energies from laser desorption. [14] Results and Discussion…”

Brominated Tyrosine and Polyelectrolyte Multilayer Analysis by Laser Desorption Vacuum Ultraviolet Postionization and Secondary Ion Mass Spectrometry

“…8,9 Both methods rely upon vacuum ultraviolet (VUV) single photon ionization (SPI) of laser desorbed or ion sputtered neutrals. 10 Recent LDPI-MS work has focused on SPI with 7.87 eV VUV radiation because it is available from a convenient laboratory source – the molecular fluorine laser which emits at 157.6 nm.…”

Comparing vacuum and extreme ultraviolet radiation for postionization of laser desorbed neutrals from bacterial biofilms and organic fullerenes

“…Vacuum ultraviolet (VUV) single photon ionization (SPI) of laser or ion desorbed neutrals has demonstrated sensitive detection and the capability for mass spectrometric imaging of atomic and molecular analytes [1–4]. Laser desorption VUV postionization mass spectrometry (LDPI-MS) of biofilms showed improved sensitivity above 8 eV photon energy with optimal signal to noise at 10.5 eV, given constant photon flux [5].…”