Photo- and Radiation Chemistry | Group Members | LEAF/Center for Radiation Chemistry Research
Brookhaven National Laboratory
Center for Radiation Chemistry Research
 |
Laser-Electron Accelerator Facility |
Features of the LEAF
The features of the new LEAF accelerator which are of most interest in comparison with those of our faithful 2 MeV electron Van de Graaff are the one-thousand-times shorter electron pulsewidth, the increased electron energy, and the picosecond synchronization of the laser and electron pulses.
Shorter Pulses
Our previous pulse radiolysis equipment is limited to studies of species living longer than 10-7 seconds (100 nanoseconds). Several new areas will be made accessible by the shorter pulses of the new machine. For example:- The study of inorganic chemistry in non-aqueous solvents.
- New studies of ion recombination in hydrocarbons.
- Measurement of very fast reaction rates.
Greater Beam Penetration
The higher energy of the LEAF accelerator (9.2 MeV) translates to increased penetration by the electron beam (about 4 g cm-2). This will permit introduction of the electron beam into high-pressure equipment (practical only for x-rays with the current equipment) and into cells in Dewar flasks for low temperature work. One important initiative enabled by the use of high pressure vessels is the study of reactions in supercritical fluids such as water or carbon dioxide. These environmentally benign materials may be of value in the reduction of pollution if they can be used in place of conventional organic solvents.
Picosecond Laser-Electron Pulse Correlation
A new and unique feature of the LEAF accelerator is the capability of a laser pulse correlated to within a picosecond of the electron pulse. Two new areas will be opened up:- The currently used techniques of picosecond spectroscopy, including continuum generation and diode-array detection, can be combined with pulse radiolysis without major modification.
- Double- and triple-beam techniques (pulse-flash-probe) can be used to examine transient species down to the femtosecond time range, i.e. the production of ions or radicals by the electron pulse followed by photoionization of a significant portion of the species by the laser pulse. The excitation laser can be used to produce a tunable beam, so that action spectra and ionization thresholds of short-lived ions can be studied.