1. 63rd International Symposium on Molecular Spectroscopy, Columbus, Ohio, June 2008 The Permanent Electric Dipole Moment of Cerium and Praesodymium Monoxides, CeO and PrO Colan Linton University of New Brunswick, Canada Jinhai Chen, Hailing Wang, Tongmei Ma and Timothy C. Steimle Arizona State University, USA Funded by: DoE_BES, NSERC

2. LnO ground states predominantly Ln 2+ [4f N σ(6s6p)]O 2- -1- Goals 1.Determine permanent electric dipole moments,  2.Determine magnetic g-factors 3.Use results from “1” & “2” to examine configurations, coupling cases and to test theory Ligand Field Theory (LFT) successful for Lanthanide Oxides and Halides CeO →Ce 2+ (4f6s)O 2- → Ω = 2: PrO → Pr(4f 2 6s)O 2- → Ω = 3.5

3. Lanthanide Oxide Dipole Moments

4. CeO transitions X 1 (Ω=2) X 2 (Ω=3) [16.5]Ω=2 R(2,3) Q(2,3) P(3,4) R(3) Q(3) P(3) 0 82 16524 T 0 (cm -1 )

5. SfSf JfJf j LfLf JaJa Ω The s electron has l=0, s=0.5, j=0.5 LFT Coupling in the Ω=2 and 3 Ground States For fs configuration: f ground state is 2 Φ 2.5 where L f =3, S f =0.5 and J f =2.5 Combining gives 2 states separated by exchange interaction Total atomic angular momentum J a =2 or 3 Ground state J a =2: 1 st excited state J a =3 Projection on axis give 2 states with Ω = 2 and 3

7. Zero Field E=1543 V/cm // E=1543 V/cm -20+2 -20+2 -20+2 ΔM J =+1 ΔM J =-1 ΔM J =0 Optical Stark Spectra of CeO [16.5]2-X 1 2 R(2)

8. The Stark shifts (first-order perturbation theory H=-  E ): -10- Results State   (D) Correlation Matrix Std. dev (MHz) X 1 2 3.119(08) 1.00 X 2 3 3.115(07) 0.40 1.00 [16.5]2 2.119(08) 0.74 0.54 1.00 8.9 Stark Analysis

10. calculated observed calculated observed Parallel Perpendicular

11. PrO transitions X 1 (Ω=3.5) X 2 (Ω=4.5) [16.6]Ω=4.5 R(3.5) F=2-1 R(4.5) F=3-2 F=4-3 0 220 16597 T 0 (cm -1 ) [18.1]Ω=5.5 18069

12. μ′ = 4.53(4)D μ″ = 2.83(3)D

13. PrO [16.6]4.5 – X 1 3.5 R(3.5) F = 2-1: Parallel Polarization F″ = 1 → 3 levels: Expect 3 Lines Observed Spectra

14. J I F MFMF J MJMJ I MIMI W Stark < W hfs J + I = F → M F 2F+1 components J=3.5, F=1 → 3 Components W Stark > W hfs J → M J 2J+1 components with structure due to M I on each component Stark and Hyperfine Coupling Schemes I → M I

15. Lanthanide Oxide Dipole Moments X CeO X PrO

16. Trend in effective nuclear charge (μ/R e )

17. Summary Dipole moments of the two lowest states of CeO are almost identical. Independent of orientation of 4f and σ(6s6p) angular momentum. Dipole moment of CeO ground state lies very close to empirical curve. PrO lowest excited state a little below curve. Stark effect of transition to PrO ground state is complex. Small hyperfine splitting in ground state leads to uncoupling of J and I by the Stark field. Work is in progress to fit the spectra.