STARK AND ZEEMAN EFFECT STUDY OF THE 18

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: Do. E (TCS) NSERC (AGA)

Previous work by Antonov and Heaven {JPC A 117, 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+(5 f 37 s 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 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′=8. 5 J′=7. 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 k. V/cm perpendicular 3. 43 k. V/cm parallel Field free

Analysis of Stark effect data Stark shift Fit Q(4. 5) and P(4. 5) Stark spectra at E = 3. 43, 3. 14, 2. 86 and 2. 57 k. V/cm with 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/Å Equivalent to nuclear charges of ~0. 20 e and 0. 19 e

Observed and Calculated Spectra of P(4. 5) Line: E = 3. 43 k. V/cm perpendicular

Zeeman Spectra of Q(4. 5 + 5. 5) Transitions Field 1. 65 k. G parallel Calc Obs 0 k. G

Analysis of Zeeman effect data Zeeman shift is given by From fit to Zeeman data in R(4. 5), Q(5. 5) at B = 1. 65 k. G with laser polarized parallel and perpendicular to magnetic field ge(X(1)4. 5) = 3. 28, ge([18. 6]3. 5)=3. 26

Interpretation of ground state g-factor (3. 28) 1. In terms of molecular 2 S+1ΛΣ States Antonov and Heaven calculated composition of ground Ω=4. 5 state 80. 74% 4Ι 4. 5 + 16. 50% 4Η 4. 5 + 2. 54% 4Γ 4. 5+ 0. 22% 4Φ 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, 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

2. In terms of parent atomic states 2 S+1 LJa For a Hund’s case (c) molecular Ω state derived from atomic 2 S+1 LJa state Ground Ω=4. 5 state of UF is derived from U+ 4 I 4. 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+ (f 3 s 2) 4 I 4. 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 4Ι 4. 5 state is 4Η 3. 5 For 4Η 3. 5 ge = 5 + 2. 002 x -1. 5 = 2 Other possibilities giving an Ω = 3. 5 state 4Γ 4Φ 4Δ (g = 3): (g = 4): 3. 5 e 3. 5 (ge = 5) Excited Ω = 3. 5 state is possibly a mixture of predominantly 4Γ 3. 5 and 4Φ 3. 5 with possibly small contributiions from 4Η 3. 5, 4Δ 3. 5 and other states

Molecular parameters for the X(1)4. 5 and [18. 6]3. 5 v = 0 states of UF State Parameter X(1)4. 5 [18. 6]3. 5 T 0 (cm-1) 0 18624. 5349(15)a B 0 (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

Conclusions 1. Field free spectra show perturbations in the upper state [18. 6]3. 5 2. Stark effect shows ground state dipole moment of 2. 01 D in excellent agreement with Antonov and Heaven calculation. Nuclear charge ~0. 2 e 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+(5 f 76 s 2 4 I 4. 5) Fconfiguration 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