61 st Symposium on Molecular Spectroscopy June 22, 2006 Completing the 3d Metal Fluoride Series: Pure Rotational Spectroscopy of ZnF (X 2  + ) Michael A. Flory Shawn K. McLamarrah Lucy M. Ziurys Department of Chemistry, Department of Astronomy, Steward Observatory University of Arizona Ti V Cr Mn Fe Co Ni Cu Zn mp °C

61 st Symposium on Molecular Spectroscopy June 22, 2006 All 3d transition metal fluorides studied in gas phase except ZnF Very few Zn molecules have been studied by high resolution spectroscopy ZnH ZnCN - Brewster and Ziurys, J. Chem. Phys., 117, 4853 (2002). ZnCH 3 - Cerny, Tan, Williamson, Robles, Ellis, and Miller, J. Chem. Phys., 99, 9376 (1993). EPR (matrix) and PES experiments previously conducted give information on fluorine hyperfine and ground state for ZnF Theoretical calculations on bonding by several authors Previous Studies - Goto, Namiki, and Saito, J. Mol. Spec., 173, 585 (1995). - Tezcan, Varberg, Stroh, and Evenson, J. Mol. Spectrosc., 185, 290 (1997). ScTiVCrMnFeCoNiCuZn F 1+1+4r4r 5r5r 6+6+7+7+6i6i 3434 2i2i 1+1+2+2+ Cl 1+1+4r4r 5r5r 6+6+7+7+6i6i 3i3i 2i2i 1+1+2+2+ 1  + : Optical data 1  + : Theory only 1  + : MW/MM data 1  + : Ziurys lab

61 st Symposium on Molecular Spectroscopy June 22, 2006 Radiation Source: Phase- locked Gunn oscillators and Schottky diode multipliers ( GHz) Gaussian beam optics utilized to minimize radiation loss Reaction Chamber: Double walled, steel cell which contains a Broida-type oven Detector: InSb bolometer Radiation is modulated at 25kHz and detected at 2f Direct Absorption Submillimeter Spectroscopy

61 st Symposium on Molecular Spectroscopy June 22, 2006 Zn vapor produced in high temp Broida-type oven – m.p. = 420 °C Reacted with excimer laser mixture – 10 %F 2 : 90 % He No d.c. discharge required No carrier gas used Initial search ~40 GHz (~4B) Synthetic problem: – Optics frequently coated in 20 min Gas-Phase Synthesis of ZnF

61 st Symposium on Molecular Spectroscopy June 22, ZnF (49%) X 2  + 64 ZnF (49%) 67 ZnF (4 %) ZnF Spectra 5 isotopomers Up to v = 3

61 st Symposium on Molecular Spectroscopy June 22, 2006 N  J  F  v (MHz) v obs-calc Sample transition frequencies for 64 ZnF (in MHz) 302 lines measured for 5 isotopomers in v = 0, 1, 2, and 3 states in frequency range GHz 64 ZnF : 66 ZnF : 67 ZnF : 68 ZnF : 70 ZnF 49 : 28 : 4 : 19 : 0.6%

61 st Symposium on Molecular Spectroscopy June 22, 2006 Hund’s case (b) effective Hamiltonian – No orbital angular momentum H eff = H Rot + H SR + H mhf(F) + H mhf( 67 Zn) + H eqQ( 67 Zn) = BN 2 +  T 1 (S). T 1 (N)+ b F T 1 (I). T 1 (S) + cT 2 (C). T 2 (S,I) + eT 2 (  E). T 2 (Q) In MHz. (Zn) Analysis Equilibrium Constants Ground State Constants

61 st Symposium on Molecular Spectroscopy June 22, 2006 In Progress 3d Halide Bond lengths Similar trends for both chlorides and fluorides “Double hump” structure as anti-bonding orbitals fill

61 st Symposium on Molecular Spectroscopy June 22, 2006 Ca bonding vs. Zn bonding –Often compared: outer 4s 2 Hyperfine parameters –electron density near nucleus –10  unpaired electron b F = Fermi contact –atomic s-orbital character c = spin-spin dipolar –atomic p-orbital character Orbital of single unpaired electron: 90% Zn(4s), 10% F(2p) – Ionic bonding Less ionic than isovalent CaF –99% Ca(4s) ZnF in MHzbFbF bFbF c 67 ZnF1290.3(1.4)317.7(3.1)539(17) atomic CaF122.6(3.5)33.3(6.9) ZnF Bonding

61 st Symposium on Molecular Spectroscopy June 22, 2006 Bonding and Equilibrium Accurate ground state potential curve Compare to several theoretical models Model by Harrison, Field, and Jarrold in near perfect agreement with experiment ZnF much more covalent than CaF, as concluded by Harrison et al. Boldyrev and Simons, Molec. Phys., 92, 365 (1997). Bowmaker and Schwerdtfeger, J. Mol. Struct. (Theochem), 205, 295 (1990). Harrison, Field, and Jarrold, ACS Symp. Series, 828 (Low-lying potential energy surfaces), 238 (2002).

61 st Symposium on Molecular Spectroscopy June 22, 2006 Conclusions Ground state is confirmed as X 2  + r e slightly longer than CuF Bonding is ionic, but less ionic than CaF Comparison with ZnCl … Tenenbaum, Flory, and Ziurys, 2007

61 st Symposium on Molecular Spectroscopy June 22, 2006 Thanks to…  Lucy Ziurys  Ziurys Group  Dr. Aldo Apponi  Dr. DeWayne Halfen  Shawn McLamarrah, Stefanie Milam, and Emmy Tenenbaum  Funding – NSF, NASA Laboratory Astronomy