Optical and Microwave Absorption Spectroscopy of Metal Containing Molecules

Funds are requested to support two visits to Prof. Maiers, group (Dept. Chemistry, University of Basel, Switzerland) at which time the mass-resolved REMPI and multiphoton ionization spectra of FeC2, and AuC2 will be recorded and analyzed. The results of those spectroscopic studies will serve as guidance for high-resolution LIF measurements to be performed at ASU. The PI and an ASU graduate student or postdoctoral fellow will participate in this project. The NSF funded project (CHE-1265885) benefits from this collaboration by utilizing the facilities at Prof. Maiers lab for rapid, and unambiguous identification of the molecules responsible for optical transitions detected in the LIF spectra recorded at ASU.

Project Summary The most fundamental electromagnetic properties, namely the permanent electric dipole moments, el , magnetic dipole moments, m , of reactive intermediates will be experimentally characterized using high resolution optical spectroscopy. Schemes for kinetic energy manipulation of molecules, as well as numerous other phenomena, require a knowledge of el and m . Furthermore, el is routinely predicted using electronic structure calculation and comparison with experimentally determined values is vital for evaluating the numerous computational methodologies being developed. el and m will be derived from the analysis spectral shifts induced by the application of either an external electric (i.e. Stark effect) or magnetic (i.e. Zeeman effect) field. Geometric (bond lengths and angles) and electronic structure (i.e. the nature of the molecular orbitals) will be optioned from analyses of the fine and magnetic hyperfine structure on the recoded optical and microwave spectra. The fine structure is readily related to the moment of inertia tensor which in turn is related to bond lengths and angles. The magnetic hyperfine structure results from the interaction of valence electrons with any non-zero nuclear spin. The nuclei act as pin-point probes of the electronic wavefunction. The molecules will be generated using either laser ablation or pulsed electrical discharge supersonic expansions. Optimum information content from our optical spectrum will be realized by using single frequency lasers to achieve the highest spectral resolution nature allows. The sensitivity required to detect these ephemeral molecules is achieve by use of single photon counting laser induced fluorescence (LIF) detection. The microwave spectra will be recorded by applying the sensitive, and selective, pump/probe microwave optical double resonance (PPMODR) scheme. In support of nuclear parity non-conservation studies being performed by others, we will record and analyze the optical field-free, Stark and Zeeman spectra and microwave spectra of ThX(X=F, S C and C2), Mg81Br and 91ZnF. The recently constructed two-color two-photon ionization spectrometer with time of flight mass selection and the existing pulsed dye laser LIF spectrometer will be used to search for these molecules prior to high resolution studies. The pure rotational spectrum of 171,173YbF will be recorded using PPMODR and analyzed. A systematic study of the properties of the 3d metal hydrides and dihydrides (MH2), is proposed. These radical species represent bound regions of the complex potential energy surface used to describe the metal activation of the H2 bond and are relevant to hydrogen storage. A proposed intersystem crossing mechanism in Si3 will be investigated by recording the dispersed LIF signal and radiative lifetimes as a function of applied magnetic field. SiH2 molecules generated in the same discharge source will be studied using optical Stark spectroscopy. Broader Impact of Research: Student and post-doctoral training in laser chemistry, molecular quantum mechanics, molecular beam and associate vacuum technology. Development of new routes for chemical synthesis of radicals relevant to chemical vapor depositions and chemical etching. Development of ultra-sensitive, optical-based, detection methods applicable to forensic science and remote sensing. Intellectual Merit: Testing and development of quantum mechanical models for description of bonding in metals. Development of effective Hamiltonians to describe highly interacting electronic states.