Double Resonance Spectroscopy of BaF Autoionizing Rydberg States Timothy J. Barnum, David Grimes, Yan Zhou, Robert W. Field Department of Chemistry, MIT ISMS – 23 June 2015

Motivation Rydberg states of highly dipolar molecules Doubly closed shell ion-core: Ba2+F- μ ~ 9 D Choice candidate for investigation by CPmmW Spectroscopy Dissociation limit > Ionization limit Detailed analysis of 4.4 ≤ n* ≤ 14.3

Previous Observations Fluorescence detection BaF effusive oven source Lowest accessible rotational state J=6.5f in C2Π3/2 intermediate state 10 core-penetrating series Several series unobservable at higher n* due to weak transition moment

Experimental Scheme D0=48200 cm-1 IPν=1=39280 cm-1 300 μJ PROBE C2Π3/2, J' IPν=0=38745 cm-1 n*~15-25, ν+=1, N+ IPν=1=39280 cm-1 D0=48200 cm-1 ~20180 cm-1 ~18600 cm-1 TOF 0.2% SF6/Ar 10 mJ / 532 nm 10 μJ PUMP 300 μJ PROBE

Intermediate State: C 2Π3/2 sR21(2.5) Conveniently about halfway between ground state and IP p~d mixed Strong transitions to Rydberg states with d and f character Pump blended rR2(X.5) + rQ21([X+1].5) lines for access to single J levels Intensity (arb. units) sR21(0.5) sR21(1.5) 20182 20184 20186 20188 Energy (cm-1)

Patterns in Spectra Δℓ=+1 propensity rule in transitions from C2Π to Rydberg states N N - 1 N - 1/2 N - 3/2 N + 1/2 N + 3/2 - + N - 5/2 2Σ+ 2Λ+ 2Λ- N - 2 N + 1 P PQ R OP Q RQ N J N - 1 N + 1 N N - 1/2 N - 3/2 N + 1/2 - + 2ΛF2 2ΛF1 P R Q OP PQ QR N – 3/2 N – 1/2 N - 1 N - 2 N + 1/2 N J J N Case (b) Case (a)

Polarization Diagnostics: Linear Excitation scheme: N” → N’=N”+1 → N Intensity ratio: Parallel/Perpendicular P R O P Q R Q Case(b) → Case(b) → Case(b) Case(b) → Case(a) → Case(b)

Polarization Diagnostics: Circular Excitation scheme: N” → N’=N”+1 → N Intensity ratio: Same helicity/Opposite helicity R R Q P Q O P Case(b) → Case(b) → Case(b) Case(b) → Case(a) → Case(b)

Polarization Diagnostics Opposite Helicity 𝐼 𝑠𝑎𝑚𝑒 𝐼 𝑜𝑝𝑝 (𝑅)> 𝐼 𝑠𝑎𝑚𝑒 𝐼 𝑜𝑝𝑝 (𝑃) R P Same Helicity

Autoionizing Spectra n*~15 n*~16 J’=9.5 J’=8.5 J’=7.5 J’=6.5 J’=5.5

Super-complex Hamiltonian 14.94 2Δ- 15.94 2Δ- 14.94 2Δ+ 15.94 2Δ+ 14.88 2Σ+ 15.88 2Σ+

Core-nonpenetrating States 14.86 2Φ 15.86 2Φ

Core-nonpenetrating States 𝑇 𝑑 𝑁 + = 𝐵 + 𝑁 + 𝑁 + +1 𝑵≡ 𝑵 + +ℓ 𝑁− 𝑁 + ≡ ℓ 𝑅 ℓ 𝑅 =−ℓ,−ℓ+1,…,+ℓ 𝑇 𝑏 𝑁 = 𝐵 + 𝑁 𝑁+1 𝑇 𝑑 𝑁, ℓ 𝑅 = 𝐵 + 𝑁− ℓ 𝑅 𝑁− ℓ 𝑅 +1 = 𝐵 + 𝑁 𝑁+1 + 𝐵 + ℓ 𝑅 ℓ 𝑅 −1 −2 𝐵 + ℓ 𝑅 𝑁 𝑇 𝑑 𝑁, ℓ 𝑅 − 𝐵 + 𝑁 𝑁+1 = 𝐵 + ℓ 𝑅 ℓ 𝑅 −1 −2 𝐵 + ℓ 𝑅 𝑁

Core-nonpenetrating States ℓ 𝑅 𝑒𝑥𝑝 =5.75 14.86 2Φ ℓ 𝑅 =6 ℓ=6 (𝑖) of

Conclusions ID-OODR on BaF Isolated states → Super-complex → MQDT 16 ID-OODR on BaF Extend analysis of core-penetrating Rydberg series Isolated states → Super-complex → MQDT Foundation for CPmmW studies of BaF Detailed analysis of core-nonpenetrating states

Questions?