| Popis: |
A progression in experimental approaches within the field of mass spectrometry is presented, with the development of two linear electrostatic ion traps. Intense, ultrashort laser pulses are used to ionise and fragment molecular gas targets in the spectrometers KEIRA and KEIRAlite, with the product ions accelerated and analysed. Integrated desorption sources of MALO and LlAD allow experiments with biologically relevant molecules that are difficult to study with conventional volatilisation and analysis techniques. Results are presented from experiments of in situ photoionisation of small organic molecules, amino acids and small peptides. A new approach to frequency analysis of the highly anharmonic signals from electrostatic trapping is introduced. The algorithm CHIMERA efficiently analyses the temporal signal to produce high resolution mass spectra with accurate identification of the different mass/charge, providing a valuable foundation for mass spectrometry experiments. Mass analysis of the molecular fragments helps identify the fundamental response of the molecules to the intense field, in order to provide information on the molecular structure and the ultrafast electron and nuclear dynamics. Complementary to the mass spectrometry experiments, the photoresponse of small peptides after resonant excitation is investigated using an action spectroscopy method in an electrostatic ion storage ring. It is demonstrated how pulse characteristics like duration, photon energy and photon flux may be defined to fundamentally alter the excitation or ionising interaction. Results are presented that show how the different interaction parameters changes the fragmentation fingerprint, where ideal parameters are identified to maximise the yield of the parent cation. The general application of ultrashort laser systems using these principles provides a tool for control in mass spectrometry experiments. Coupling this with the high resolution capabilities of the KEIRA spectrometers, a foundation has been laid for exciting experiments in this expanding research field. |
