61 st symposium on molecular spectroscopy june 22, 2006 completing the 3d metal fluoride series:...

61st 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

1670 1910 1863 1246 1538 1495 1445 1085 420mp °C


• 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).

• ZnCH3 - 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).

Sc Ti V Cr Mn Fe Co Ni Cu Zn

F 1+ 4r5r

6+ 7+ 6i34

2i1+ 2+

Cl 1+ 4r5r

6+ 7+ 6i3i

2i1+ 2+

1+ : Optical data1+ : Theory only1+ : MW/MM data1+ : Ziurys lab


• Radiation Source: Phase-locked Gunn oscillators and Schottky diode multipliers (65-660 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


• Zn vapor produced in high temp Broida-type oven

– m.p. = 420 °C • Reacted with excimer laser mixture

– 10 %F2 : 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


64ZnF(49%)X 2+

64ZnF(49%)

67ZnF(4 %)

ZnF Spectra5 isotopomersUp to v = 3


N J F v (MHz) vobs-calc

Sample transition frequencies for 64ZnF (in MHz)

302 lines measured for 5 isotopomers in v = 0, 1, 2, and 3 states in frequency range 175-527 GHz

64ZnF : 66ZnF : 67ZnF : 68ZnF : 70ZnF 49 : 28 : 4 : 19 : 0.6%


• Hund’s case (b) effective Hamiltonian – No orbital angular momentum

Heff = HRot + HSR + Hmhf(F) + Hmhf(67Zn) + HeqQ(67Zn)

• = BN2 +T1(S).T1(N)+ bFT1(I).T1(S) + cT2(C).T2(S,I) + eT2(E).T2(Q)

In MHz.

(Zn)

Analysis

Equilibrium ConstantsGround State Constants


In Progress

3d Halide Bond lengths

Similar trends for both chlorides and fluorides“Double hump” structure as anti-bonding orbitals fill


• Ca bonding vs. Zn bonding

– Often compared: outer 4s2

• Hyperfine parameters

– electron density near nucleus

– 10 unpaired electron

• bF = 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)

Zn F

in MHz bF bF c

67ZnF 1290.3(1.4) 317.7(3.1) 539(17)

atomic 1425.6 47910 4545

CaF 122.6(3.5) 33.3(6.9)

ZnF Bonding


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).


Conclusions• Ground state is confirmed as X 2+

• re slightly longer than CuF• Bonding is ionic, but less ionic than CaF

Comparison with ZnCl …Tenenbaum, Flory, and Ziurys, 2007


Thanks to… Lucy Ziurys

Ziurys Group Dr. Aldo Apponi Dr. DeWayne Halfen Shawn McLamarrah,

Stefanie Milam, and Emmy Tenenbaum

Funding – NSF, NASA Laboratory Astronomy

61 st symposium on molecular spectroscopy june 22, 2006 completing the 3d metal fluoride series:...

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