1. Electron Spin Resonance Investigations of Matrix Isolated Metal Clusters at 4 K
Bradford Michael Mess, John J. Banisaukas III, and Lon B. Knight, Jr.
Department of Chemistry, Furman University, Greenville, SC

2. Introduction
Studying metal clusters is necessary to understand the transition from atomic and molecular properties to metallic bulk properties
Metal clusters also play an important role in developing new catalysts

3. Formation of Metal Clusters
Laser Vaporization
Thermal Vaporization hν
copper electrodes
metal atoms
metal atoms
metal sample
tantalum tube
Cluster size depends on:
Concentration ratio of rare gas to metal vapor
Deposition temperature

4. Deposition Site Metal atom Neon atom Cluster formation
Copper target cooled to 4 K

5. Matrix Isolation Apparatus
Gases used:
neon
argon
methane
Background pressure:
8 x 10-7 Torr
Liquid helium cryostat
Metals used:
magnesium
calcium
zinc
8 cm
copper electrodes

6. Magnesium and Calcium Experiments
Conditions
Deposited in:
neon
argon
methane
Deposit length:
1 hour
Mg deposits
Dilute: grayish-red
Medium: dark red
Heavy; dark gray
Flow rates:
2.4 – 5.0 sccm
Deposit temperatures:
4 – 40 K
Ca deposits
All: gray black
Goal: Maximize high spin species

7. ESR spectra of high spin Mg neutral clusters in neon at 4 K
no hyperfine – due to π-bonding
g┴ = 1.996(1) g║ = 2.000(1) D (zfs) = 2645(5) MHz

8. ESR spectra of high spin Ca neutral clusters in neon at 4 K
Signals only seen in neon

9. Zinc Experiments Conditions Deposited in: neon Deposit length: 1 hour
Zn deposits
Dilute: colorless/light orange
Medium: dark orange
Heavy; black
Average flow rate:
4.4 sccm
Goal: control the size of clusters
Deposit temperatures:
4 – 40 K
X – irradiation:
30 minutes at 60 keV

10. ESR spectra of zinc dimer and trimer cations in neon at 2.6 K
67Zn+ (4.11 % abundance)
I = 5/2
Deposit temperature: 2.6 K
Higher Zn concentration
Lower Zn concentration

11. Magnetic parameters (MHz) of zinc monomer, dimer, and trimer, cation radicals

12. Relative line positions of zinc cations

13. Acknowledgments
Thank you to:
Dr. Knight TJ
Grant Hendrickson