63rd International Symposium on Molecular Spectroscopy, Columbus, Ohio, June 2008

The Permanent Electric Dipole Moment of Cerium and Praesodymium Monoxides, CeO and PrO

Colan LintonUniversity of New Brunswick, Canada

Jinhai Chen, Hailing Wang, Tongmei Ma and Timothy C. SteimleArizona State University, USA

Funded by: DoE_BES, NSERC

LnO ground states predominantly Ln2+[4fNσ(6s6p)]O2-

-1-

Goals 1. Determine permanent electric dipole moments, 2. Determine magnetic g-factors3. 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 →Ce2+(4f6s)O2- → Ω = 2: PrO → Pr(4f26s)O2- → Ω = 3.5

NdO

Lanthanide Oxide Dipole Moments

CeO transitions

X1(Ω=2)

X2(Ω=3)

[16.5]Ω=2

R(2,3)Q(2,3)P(3,4)

R(3)Q(3)P(3)

0

82

16524T0(cm-1)

Sf

Jf

j

Lf Ja

Ω

The s electron has l=0, s=0.5, j=0.5

LFT Coupling in the Ω=2 and 3 Ground StatesFor fs configuration: f ground state is 2Φ2.5

where Lf=3, Sf=0.5 and Jf=2.5

Combining gives 2 states separated by exchange interaction

Total atomic angular momentum Ja=2 or 3

Ground state Ja=2: 1st excited state Ja=3

Projection on axis give 2 stateswith Ω = 2 and 3

PerpendicularParallel

Stark Effect in R(2) Transition

2

3

JM

X12

[16.5]2

M -1+10

-3

0

3

-202

Zero Field

E=1543 V/cm //

E=1543 V/cm-500 0 500

Stark Shift (MHz)

-2 0 +2

-2 0 +2

-2 0 +2

ΔMJ=+1ΔMJ=-1

ΔMJ=0

Optical Stark Spectra of CeO [16.5]2-X12 R(2)

2

3

JM

X12

[16.5]2

M -1+10

-3

0

3

-202

MHz/D)5034.0()1(Ω

Stark

JJ

μEM J

The Stark shifts (first-order perturbation theory H=-E ):

-10-

ResultsState (D) Correlation Matrix Std. dev (MHz)

X12 3.119(08) 1.00

X23 3.115(07) 0.40 1.00

[16.5]2 2.119(08) 0.74 0.54 1.00 8.9

Stark Analysis

-1200-1000 -800 -600 -400 -200 0 200 400 600 800 1000 1200

calculated

observed

CeO Stark Spectrum [16.5]2-X12 R2 Perpendicular 1033V/cm

Stark Shift (MHz)

-1000 -500 0 500 1000

CeO Stark Spectrum [16.5]2 - X23 Q(3) 970 V/cm

Stark Shift (MHz)

calculated

observed

calculated

observed

J=3

J=3

X23

[16.5]2

M -1+10

-3

0

3

-3

0

3

Parallel

Perpendicular

PrO transitions

X1(Ω=3.5)

X2(Ω=4.5)

[16.6]Ω=4.5

R(3.5)F=2-1

R(4.5)F=3-2F=4-3

0

220

16597

T0(cm-1)

[18.1]Ω=5.518069

-1200-1000 -800 -600 -400 -200 0 200 400 600 800 1000 1200

Perpendicular

Parallel

981 V/cm

Zero Field

PrO [18.1]5.5 - X24.5 R(4.5) F= 3-2

Stark Shift (MHz)

μ′ = 4.53(4)Dμ″ = 2.83(3)D

-1000 -800 -600 -400 -200 0 200 400 600 800 1000

528 V/cm

377 V/cm

302 V/cm

Stark Shift (MHz)

PrO [16.6]4.5 – X13.5 R(3.5) F = 2-1: Parallel PolarizationF″ = 1 → 3 levels: Expect 3 Lines

Observed Spectra

J

I

F

MF

J

MJ

I

MI

WStark < Whfs

J + I = F → MF

2F+1 components

J=3.5, F=1 → 3 Components

WStark > Whfs

J → MJ

2J+1 components with structuredue to MI on each component

Stark and Hyperfine Coupling Schemes

I → MI

NdO

Lanthanide Oxide Dipole Moments

XCeO X

PrO

Trend in effective nuclear charge (μ/Re)

-2 0 2 4 6 8 10 12 14

0.30

0.35

0.40

0.45

0.50

0.55

0.60

0.65

0.70

0.75

CeO

PrO

YbO

HoO

DyO

SmOLaO

NdO

/R

e (un

its o

f e)

No of f-electrons

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.