The Submillimeter Spectrumof UO

Jennifer A. HoltChristopher F. Neese

Frank C. De Lucia

June 17, 2014

Experimental Setup

High Temperature Furnace

Vacuum

Water cooled shield

Radiation Shields

Furnace Tube

Power Supply

Production of NdO vs UO

• High temperature decomposition of Nd2O3

– ~2200K– Run times of ~3 hours

• UO from mixed metal and oxide– Starts with mixed metal and oxide– Highly aggressive to furnace– Short runtimes of ~20 minutes– Temperature ~2000K

Experimental Changes for UO

• Graphite tube with tungsten liner and Y2O3 painted coating– Increased furnace durability and runtimes– Increased S/N

• Sample consists of U metal with UO2 Powder– Materials mixed and pressed into pellet– Pellet placed in the center of the furnace tube

Graphite Furnace Tube

Spectral Coverage

Example Lines

(1)3(v=0)R31

Spectroscopy of UO vs NdO

• NdO has 3 isotopes with similar natural abundance, UO has one.

• UO has a second low lying electronic configuration.

J. Chem. Phys. 124, 184317 (2006)© 2006 American Institute of Physics Kaledin et al., J. Mol. Spectr. 164, 27-64 (1994)

UO LFT

• UO is a Hund’s case C molecule, (minimal information).• LFT gives an alternate description with a U2+ cation perturbed by a O2- ligand.• U2+ has two low lying electronic configurations: [5f37s], [5f27s2].• Approximate quantum numbers Jf and Ja from SO and J-J coupling.• LFT allows for the calculation of an energy map of the low lying electronic states.

Hund’s Case C Coupling

Energy Map

Kaledin et al., J. Mol. Spectr. 164, 27-64 (1994)

Line AssignmentsVibronic State B (GHz) D (KHz) σν (KHz)

(1)3(v=0) 9.83126 5.86886 26.2

(1)3(v=1) 9.79056 5.90674 7.35

(1)3(v=2) 9.75022 5.93979 39.2

(1)3(v=3) 9.71000 5.92876 63.7

(1)5(v=0) 9.89349 6.03838 43.6

(1)5(v=1) 9.85354 6.0681 19.6

(1)5(v=2) 9.82475 5.40802 40.4

(1)5(v=3) 9.79889 5.51045 32.3

X4(v=0) 9.99278 10.2945 470

X4(v=1) 9.89609 6.96244 254

X4(v=2) 9.84015 5.7619 15.9

(2)4(v=0) 10.3778 2.14331 372

(2)4(v=1) 10.3889 5.81611 172

[5f37s]

[5f27s2]

UO Line Stats

• 285 observed lines from 510 GHz to 652 GHz• 13 series identified and assigned• 3 series identified, but not assigned• 200 unassigned lines

Ongoing work

• Continue line assignments• Dunham fits over vibrational states

Acknowledgements

• Michael Heaven• Ivan Medvedev

We would also like to thank the Missile Defense Agency and the Army Research Office for their support of this work

Supplemental Slides

Material Properties (W)

• Highest melting point metal: 3695K• Very hard and brittle• Difficult to work• Does not spot-weld with any equipment we

have• Moderately expensive

Material Properties (Mo)

• Melting point 2896K• Softer and more ductile than tungsten• Can spot-weld with difficulty• Fairly inexpensive

Material Properties (Ta)

• Melting point 3290K• Very ductile and easy to work• Easily spot-welds• Expensive

Material Graphite (C)

• Sublimation point 3915K• Machines easily, but very brittle• Conductivity lower than metals, allows better

electrical match to power supply• Forms carbides with U at high temperatures• Reacts with Y2O3 at high temperatures

Material Yttria (Y2O3)

• Melting point 2698K• Very stable chemically, holds up well to

molten uranium• Reacts with carbon at high temperatures• Transparent in SMM region