Femtosecond Pump-Probe Experiments with a High Repetition Rate Molecular Beam

Abstract

This paper describes the first results in the field of femto chemistry obtained by our group at the VUA. A high repetition rate (1 KHz) molecular beam machine and laser system have been used. The laser system was supplied by Spectra Physics and consists of a chirped amplified titanium sapphire system. Its source, formed by a titanium sapphire oscillator (Tsunami) produces 70 fs pulses with a repetition rate of 82 MHz and an energy of approximately 10 nJ per pulse. The output is tunable between 760 nm and 820 nm. A homebuilt autocorrelator was used to determine the pulse duration of the oscillator. The autocorrelator is based on a Michelson-type interferometer with a Hamamatsu photodiode as detector[1]. The semi conductor detector has a bandgap exceeding the energy of one photon of 800 nm, so a two photon process is needed to generate a signal. The measured pulse duration of 70 fs (FWHM) shown in Fig.1 is in agreement with the specified value of the Tsunami.