63 rd International Symposium on Molecular Spectroscopy Columbus

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

Goals 1. Determine permanent electric dipole moments, m 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 Ln. O ground states predominantly Ln 2+[4 f. Nσ(6 s 6 p)]O 2 Ce. O →Ce 2+(4 f 6 s)O 2 - → Ω = 2: Pr. O → Pr(4 f 26 s)O 2 - → Ω = 3. 5 -1 -

Lanthanide Oxide Dipole Moments

Ce. O transitions T 0(cm-1) 16524 [16. 5]Ω=2 R(2, 3) Q(2, 3) P(3, 4) R(3) Q(3) P(3) 82 X 2(Ω=3) 0 X 1(Ω=2)

LFT Coupling in the Ω=2 and 3 Ground States For fs configuration: f ground state is 2Φ 2. 5 where Lf=3, Sf=0. 5 and Jf=2. 5 The s electron has l=0, s=0. 5, j=0. 5 Combining gives 2 states separated by exchange interaction Total atomic angular momentum Ja=2 or 3 Ground state Ja=2: 1 st excited state Ja=3 Projection on axis give 2 states with Ω = 2 and 3 Sf j Jf Lf Ja Ω

Optical Stark Spectra of Ce. O [16. 5]2 -X 12 R(2) Zero Field -2 E=1543 V/cm // ΔMJ=+1 E=1543 V/cm 0 -2 -2 +2 0 0 ΔMJ=0 +2 +2 ΔMJ=-1

Stark Analysis The Stark shifts (first-order perturbation theory H=-m. E ): Results State (MHz) (D) Correlation Matrix X 12 3. 119(08) 1. 00 X 23 3. 115(07) 0. 40 1. 00 [16. 5]2 2. 119(08) 0. 74 0. 54 -10 - 1. 00 Std. dev 8. 9

Parallel calculated observed Perpendicular calculated observed

Pr. O transitions T 0(cm-1) 18069 [18. 1]Ω=5. 5 16597 [16. 6]Ω=4. 5 R(3. 5) F=2 -1 R(4. 5) F=3 -2 F=4 -3 220 X 2(Ω=4. 5) 0 X 1(Ω=3. 5)

Pr. O [16. 6]4. 5 – X 13. 5 R(3. 5) F = 2 -1: Parallel Polarization F″ = 1 → 3 levels: Expect 3 Lines Observed Spectra

Stark and Hyperfine Coupling Schemes I WStark < Whfs J + I = F → MF J F 2 F+1 components J=3. 5, F=1 → 3 Components MF WStark > Whfs J I MJ MI J → MJ I → MI 2 J+1 components with structure due to MI on each component

Lanthanide Oxide Dipole Moments X Ce. O X Pr. O

Trend in effective nuclear charge (μ/Re)

Summary • Dipole moments of the two lowest states of Ce. O are almost identical. Independent of orientation of 4 f and σ(6 s 6 p) angular momentum. • Dipole moment of Ce. O ground state lies very close to empirical curve. Pr. O lowest excited state a little below curve. • Stark effect of transition to Pr. O 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.