stark and zeeman effect study of the [18.6]3.5 – x(1)4.5 band of uranium monofluoride, uf colan...

STARK AND ZEEMAN EFFECT STUDY OF THE [18.6]3.5 – X(1)4.5 BAND OF URANIUM MONOFLUORIDE, UF

COLAN LINTON, ALLAN G. ADAMUniversity of New Brunswick

TIMOTHY C. STEIMLEArizona State University

Funding: DoE (TCS) NSERC (AGA)

Previous work by Antonov and Heaven JPC A117, 9684 (2013)

Experiment:

Analysis of pulsed laser excitation spectrum of [18.6]3.5-X(1)4.5 transition of UF

Ground Ω = 4.5 state is derived from U+(5f37s2 4I4.5) F- configuration

Theory:

Calculations of excited state term energies in good agreement with experiment

Calculated dipole moment of ground state μel = 1.99 Debye

Calculated composition of ground Ω=4.5 state in terms of ΛS case (a) states

Present Work• High resolution (FWHM ≤ 40 MHz) experiments at ASU• 50 fold improvement in resolution over previous experiments• Rotational analysis of [18.6]3.5 – X(1)4.5 0 - 0 band• Stark effect to determine dipole moments• Zeeman effect to determine configurational composition of electronic states• Use above to test theoretical predictions

Q branch of the [18.6]3.5 – X(1)4.5 transition of UF

Two extra lines for J′ ≥ 7.5: Upper state is perturbed

P(J′+1)Q(J′)R(J′-1)

J′=7.5

J′=8.5 J′=9.5

Stark Spectra of the P(4.5) Line of the [18.6]3.5 – X(1)4.5 transition of UF

3.43 kV/cm perpendicular

3.43 kV/cm parallel

Field free

)/5034.0()1(

DMHzJJEM Jel

Stark

Stark shift

Fit Q(4.5) and P(4.5) Stark spectra at E = 3.43, 3.14, 2.86 and 2.57 kV/cmwith laser polarized parallel and perpendicular to electric field gave

μel(X(1)4.5) = 2.01(1)D μel([18.6]3.5) = 1.88(1) D

Obs. and calc. ground state dipole moments in excellent agreement.

Reduced dipole moments μel/Re = 0.99 and 0.92 D/ÅEquivalent to nuclear charges of ~0.20e and 0.19e

Analysis of Stark effect data

Observed and Calculated Spectra of P(4.5) Line: E = 3.43 kV/cm perpendicular

Zeeman Spectra of Q(4.5 + 5.5) Transitions

Obs

CalcField

1.65 kGparallel

0 kG

)1(399.1

JJBMg Je

ZeeZeeman shift is given by

From fit to Zeeman data in R(4.5), Q(4.5), Q(5.5) at B = 1.65 kGwith laser polarized parallel and perpendicular to magnetic field

ge(X(1)4.5) = 3.28, ge([18.6]3.5)=3.26

Analysis of Zeeman effect data

Interpretation of ground state g-factor (3.28)1. In terms of molecular 2S+1ΛΣ States

Antonov and Heaven calculated composition of ground Ω=4.5 state 80.74% 4Ι4.5 + 16.50% 4Η4.5 + 2.54% 4Γ4.5+ 0.22% 4Φ4.5

(Λ=6, Σ=-1.5) (Λ=5, Σ=-0.5) (Λ=4, Σ=+0.5) (Λ=3, Σ=+1.5)

For Hund’s case (a) states, ge = (Λ + 2.002Σ) giving a calculated g-factor ge = 0.8074 x 3 + 0.1650 x 4 + 0.0254 x 5 + 0.0022 x 6 = 3.22

Calculation in very good agreement with experiment

)1(2

)1()1()1(1

aa

aae JJ

LLSSJJg

2. In terms of parent atomic states 2S+1LJa

For a Hund’s case (c) molecular Ω state derived from atomic 2S+1LJa state

Ground Ω=4.5 state of UF is derived from U+ 4I4.5 state L = 6, S= 1.5, Ja = 4.5, Ω = 4.5

ge (calc) = 3.27 ge (exp) = 3.28

Molecular ground state derived entirely from U+ (f3s2) 4I4.5 state

Excited [18.6]3.5 State (ge = 3.26):

Transition is Ω = 3.5 – 4.5.Logical choice for ΔΩ = -1 transition to predominantly 4Ι4.5 state is 4Η3.5

For 4Η3.5 ge = 5 + 2.002 x -1.5 = 2

Other possibilities giving an Ω = 3.5 state 4Γ3.5 (ge = 3): 4Φ3.5 (ge = 4): 4Δ3.5 (ge = 5)

Excited Ω = 3.5 state is possibly a mixture of predominantly 4Γ3.5 and 4Φ3.5 with possibly small contributiions from 4Η3.5, 4Δ3.5 and other states

State

Parameter X(1)4.5 [18.6]3.5

T0 (cm-1) 0 18624.5349(15)a

B0 (cm-1) 0.23247(3) 0.22754(3)a

μel (Debye) 2.01(1) 1.88(1)

ge 3.28(1) 3.26(1)

a From fit to lowest 4 levels

Molecular parameters for the X(1)4.5 and [18.6]3.5 v = 0 states of UF

Conclusions1. Field free spectra show perturbations in the upper state [18.6]3.5

2. Stark effect shows ground state dipole moment of 2.01D in excellent agreement with Antonov and Heaven calculation. Nuclear charge ~0.2e 3. Zeeman effect shows that (i) the calculated compostion of the X(1)4.5 ground state in terms of Hund’s case (a) ΛS states reproduces the observed electronic g-factor very well. (ii) The ground state arises almost entirely from the U+(5f76s2 4I4.5) F- configuration

4. The discussion on the upper state configuration is highly speculative. The g-factor suggests possible configurations and eliminates others .

5. More theoretical calculations are needed