An Advantage of the Equivalent Velocity Spectroscopy for Femtosecond Pulse Radiolysis

For studies of electron beam induced ultra-fast reaction process, femtosecond (fs) pulse radiolysis is under construction. To realize fs time resolution, fs electron and analyzing light pulses and their jitter compensation system are needed. About a 100fs electron pulse was generated by a photocathode RF gun LINAC and a magnetic pulse compressor. Synchronized Ti: Sapphire laser have a pulse width about 160fs. And, it is significant to avoid degradation of time resolution caused by velocity difference between electron and analyzing light in a sample. In the ‘Equivalent velocity spectroscopy’ method, incident analyzing light is slant toward electron beam with an angle associated with refractive index of sample. Then, to overlap light wave front and electron pulse shape, electron pulse shape is slanted toward the direction of travel. As a result of the equivalent velocity spectroscopy for hydrated electrons, using slanted electron pulse shape, optical absorption rise time was about 1.4ps faster than normal electron pulse shape. Thus, the ‘Equivalent velocity spectroscopy’ is effective for femtosecond pulse radiolysis.