Ph.D Thesis


Ph.D StudentFisher Danny
SubjectAnalytical Chemistry Applications of Multiphoton Electron
Extraction Spectroscopy (MEES)
DepartmentDepartment of Chemistry
Supervisor PROF. Israel Schechter


Abstract

Many analytical spectroscopy tools are available, but almost none is based on measuring electrical charge as a function of irradiation wavelength. Not only that, similar attempts to obtain such data usually required operation under high vacuum conditions. Muliphoton Electron Extraction Spectroscopy (MEES) is an analytical method that measures the photo-electrons emitted from molecules in a multiphoton process, as a function of  laser wavelength, under ambient conditions. Whenever the energy of a photon, or a combination of photons, is in resonance with a molecular energy level of the analyte, the current increase. The time integrated current, namely the photocharge is presented as a function of laser wavelength. This study aimed to prove the potential of MEES as an analytical spectroscopy tool for various applications.

MEES study was focused on: (1) identification and selective detection of energetic materials, as well as other NOx based molecules. (2) investigation of the isotopic shifts in 14/15N, 16/18O and 32/34S. (3) application of MEES to examination of inks and printed matter. (4) application of MEES to detection of counterfeit banknotes (5) application of MEES to food products. (6) application of MEES to pharmaceuticals inspection and detection of medication impurities.

Our findings include the following:

         New MEES spectra of N-oxides and several energetic materials such as: HNS, CL-20, TEX and more. The MEES data were discussed and explained.

         Isotopic shift in MEES was thoroughly presented and discussed.

         MEES can potentially be used as a forensic tool for identification of counterfeit money.

         MEES can be used to detect traces of date-rape drug in Whisky.

         2-nitrotoluene was used as a model compound for MEES detection of vapours.