1. 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

2. 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

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

4. 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

5. 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)

6. 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)

7. 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)

8. 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)

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

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

11. Super-complex HamiltonianΔ- Δ- Δ+ Δ+ Σ+ Σ+

12. Core-nonpenetrating StatesΦ Φ

13. 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

14. Core-nonpenetrating States
ℓ 𝑅 𝑒𝑥𝑝 =5.75 Φ
ℓ 𝑅 =6
ℓ=6 (𝑖) of

15. Conclusions ID-OODR on BaF Isolated states → Super-complex → MQDT16
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

16. Questions?