Application of stimulated Raman pumping toward the first study of chemical reaction dynamics of the muonium atom with H(2)(star)

The chemical reaction of interest, from the field of mu SR spectroscopy, is that of the muonium atom (Mu) with molecular hydrogen in its first vibrational excited state. The stimulated Raman pumping (SRP) technique has been used to prepare H(2) in its nu = 1 state in a series of off-line experiments at the LASIR Lab at UBC. Three different SRP excitation schemes employing the second harmonic of a Nd:YAG laser have been analysed in connection with this application, for 5.5, 13, and 26 cm-long reaction cells. The laser energy varied from similar to 80 to similar to 550 mJ/pulse (or from similar to 0.07 GW/cm(2) to similar to 0.46 GW/cm(2)) at a 10 Hz repetition rate. The importance of injection seeding of the Nd: YAG laser for efficient molecular excitation is shown. The major challenge of this experiment was to ensure a homogeneous excitation over a large volume (few cm 3) while achieving a high amount of vibrationally excited H(2) (3-15 Torr). This is demanded by the requirements of superposition of a pulsed muon beam with the laser beam and the expected rate constant of the Mu + H(2)(star)(nu = 1) –> MuH + H reaction. In this endeavour it was also of interest to explore the effect of added moderator gas to the hydrogen and so the effect of Ar/Xe moderator on the efficiency of hydrogen pumping for different SRP excitation schemes is also shown.