STARK AND ZEEMAN EFFECT STUDY OF THE [18.6]3.5 – X(1)4.5 BAND OF URANIUM MONOFLUORIDE, UF COLAN LINTON, ALLAN G. ADAM University of New Brunswick TIMOTHY C. STEIMLE Arizona 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 + (5f 3 7s 2 4 I 4.5 ) F - configuration Theory: Calculations of excited state term energies in good agreement with experiment Calculated dipole moment of ground state μ el = 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) 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′=8.5J′=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

Stark shift Fit Q(4.5) and P(4.5) Stark spectra at E = 3.43, 3.14, 2.86 and 2.57 kV/cm with laser polarized parallel and perpendicular to electric field gave μ el (X(1)4.5) = 2.01(1)D μ el ([18.6]3.5) = 1.88(1) D Obs. and calc. ground state dipole moments in excellent agreement. Reduced dipole moments μ el /R e = 0.99 and 0.92 D/Å Equivalent 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( ) Transitions Obs Calc Field 1.65 kG parallel 0 kG

Zeeman shift is given by From fit to Zeeman data in R(4.5), Q(4.5), Q(5.5) at B = 1.65 kG with laser polarized parallel and perpendicular to magnetic field g e (X(1)4.5) = 3.28, g e ([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+1 Λ Σ States Antonov and Heaven calculated composition of ground Ω=4.5 state 80.74% 4 Ι % 4 Η % 4 Γ % 4 Φ 4.5 (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, g e = (Λ Σ) giving a calculated g-factor g e = x x x x 6 = 3.22 Calculation in very good agreement with experiment

2. In terms of parent atomic states 2S+1 L Ja For a Hund’s case (c) molecular Ω state derived from atomic 2S+1 L Ja state Ground Ω=4.5 state of UF is derived from U + 4 I 4.5 state L = 6, S= 1.5, J a = 4.5, Ω = 4.5 g e (calc) = 3.27 g e (exp) = 3.28 Molecular ground state derived entirely from U + (f 3 s 2 ) 4 I 4.5 state

Excited [18.6]3.5 State (g e = 3.26): Transition is Ω = 3.5 – 4.5. Logical choice for ΔΩ = -1 transition to predominantly 4 Ι 4.5 state is 4 Η 3.5 For 4 Η 3.5 g e = x -1.5 = 2 Other possibilities giving an Ω = 3.5 state 4 Γ 3.5 (g e = 3): 4 Φ 3.5 (g e = 4): 4 Δ 3.5 (g e = 5) Excited Ω = 3.5 state is possibly a mixture of predominantly 4 Γ 3.5 and 4 Φ 3.5 with possibly small contributiions from 4 Η 3.5, 4 Δ 3.5 and other states

State ParameterX(1)4.5[18.6]3.5 T 0 (cm -1 ) (15) a B 0 (cm -1 ) (3) (3) a μ el (Debye)2.01(1)1.88(1) gege 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

Conclusions 1. Field free spectra show perturbations in the upper state [18.6] 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 + (5f 7 6s 2 4 I 4.5 ) 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