Knowledge Bank

A long path-length (20 cm), multipass (40x), magnetically confined, sputter source has been designed for laser spectroscopic studies of metal hydride, halide, and oxide diatomic molecules. The source consists of a cylindrical cathode of the metal to be vaporized and 10 sequential anodes (resistively and inductively stabilized). An axial 1-2 kG magnetic field confines the Ar+ glow discharge and increases the sputtering efficiency 3-10-fold and allows stable operation of the device at pressures as low as 50 mTorr. Laser beams propagate directly through the discharge region where the MX molecules are generated. The 20 cm absorption length may be multiplied by at least 40x by an internal mirror White cell multipass arrangement. The new source is superior to the single anode sputter sources used previously in studies of NiH in providing higher molecule number density, 400x longer absorption length, $>5x$ lower operating pressure, and improved discharge stability. It is well suited to studies of refractory metal containing molecules in which the signal is carried by the transmitted laser beam (direct absorption, magnetic rotation, polarization, transient nutation, and homodyne spectroscopies) rather than laser excited fluorescence. Magnetic rotation and absorption spectra of the weak NiH $\Omega =3/2v=1+X2\Delta 5/2v=0$ band and sub-Doppler polarization spectra of the -30x stronger $NiHB2\Delta 5/2v=1+X2\Delta 5/2v=0$ band have been recorded. The capabilities of this source are still being evaluated, but it appears to be more sensitive by $>103$ than Broida oven and single anode sputter sources.