High resolution spectroscopy of transient metal-containing diatomic molecules.

摘要

The near-infrared and visible band systems of the diatomic molecules CaH, FeO, ScS, MnH, RhO, and RhN have been studied utilizing high resolution spectroscopy. Most of these metal-containing species are free radicals and as such provide edifying spectra from which information regarding electronic structure can be gleaned. Directly accessible phenomena modeled by effective Hamiltonian methods are molecular rotation, spin-orbit, spin-spin, spin-rotation, lambda-doubling, magnetic hyperfine interactions, and electric quadrupole interactions. In the case of CaH a deperturbation analysis was performed and in the case of RhN isotopic substitution was analyzed. For CaH, FeO, RhO, and RhN, the application of an external static electric field i.e. Stark effect) allowed determination of permanent electric dipole moments of the ground and excited states probed. For CaH and MnH, the application of an external static magnetic field (i.e. Zeeman effect) allowed determination of effective g-factors. Parameters obtained from the data indirectly allow a description of the molecular orbitals involved, and were also compared to ab initio calculations. Due to the transient nature of these gas phase molecules, production was accomplished via laser ablation of a metal sample and introduction of an appropriate reagent gas. Subsequent supersonic expansion and molecular beam formation then allowed probing of the molecules by Laser Induced Fluorescence (LIF). High-resolution spectra were facilitated by a Continuous-Wave (CW) ring laser. Complementary to this, low or medium resolution spectra were obtained with a pulsed-dye laser (controlled via a homemade Visual Basic 6.0 computer program). Several previously unobserved band systems have been detected as part of a project involving survey scans of Rh metal plus various gas reagents including CH4, SF6, NH3, and D2.