Electron pulse-probe analysis

Laser ionization mass spectrometry or laser microprobing (LIMS) is a microanalyt-ical technique used to rapidly characterize the elemental and, sometimes, molecular composition of materials. It is based on the ability of short high-power laser pulses (-10 ns) to produce ions from solids. The ions formed in these brief pulses are analyzed using a time-of-flight mass spectrometer. The quasi-simultaneous collection of all ion masses allows the survey analysis of unknown materials. The main applications of LIMS are in failure analysis, where chemical differences between a contaminated sample and a control need to be rapidly assessed. The ability to focus the laser beam to a diameter of approximately 1 mm permits the application of this technique to the characterization of small features, for example, in integrated circuits. The LIMS detection limits for many elements are close to 10 at/cm, which makes this technique considerably more sensitive than other survey microan-alytical techniques, such as Auger Electron Spectroscopy (AES) or Electron Probe Microanalysis (EPMA). Additionally, LIMS can be used to analyze insulating sam-... 

The determination of copper is also discussed under Multi-Metal Analysis of Soils in Sect. 2.55 (atomic absorption spectrometry), Sect. 2.55 (emission spectrometry), Sect. 2.55 (inductively coupled plasma atomic emission spectrometry), Sect. 2.55 (photon activation analysis), Sect. 2.55 (neutron activation analysis), Sect. 2.55 (electron probe microanalysis) and Sect. 2.55 (differential pulse anodic stripping voltammetry). 

More recently, the use of picosecond and femtosecond lasers in reaction dynamics opened up the field of femtochemistry, which was pioneered by Zewail [51-54]. The idea of these reactions is to photoinitiate the reactive process in a van der Waals complex. Sometimes, the process that is initiated is a simple dissociation or the isomerization of a free molecule. In each case, the reaction is initiated by a first ultrashort laser pulse (the pump pulse). It is analyzed after a certain delay by a second pulse (the probe pulse). This gives access to the reaction dynamics on the pertinent time-scale where chemical bonds are broken and others are formed. Depending on the system, this typically lasts between a few tenths of femtoseconds to hundredths of picoseconds. Recently the techniques of stereodynamies have been combined by Zewail and co-workers with femtosecond analysis [55, 56] to label specific reaction channels in electron-transfer reactions. 

---