selective population of core nonpenetrating rydberg states david grimes, yan zhou, timothy j barnum,...
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Selective population of Core Nonpenetrating Rydberg statesDavid Grimes, Yan Zhou, Timothy J Barnum, Ethan Klein, Robert FieldDepartment of Chemistry, MIT
Outline
• Introduction to core nonpenetrating (CNP) Rydberg states
• Why CNP states are useful• Using chirped pulse millimeter wave
(CPmmW) spectroscopy to access and identify these states
• The difficulties in accessing these states in most molecules
• Using CPmmW spectroscopy to overcome the obstacles 2
What are Core Nonpenetrating States?
3
N+N
Λ
( )ℓ
N+
N
ℓ
• Centrifugal barrier prevents overlap with the core• Nonradiative decay mechanisms (autoionization,
predissociation) scale as overlap with the core (n-3, exponentially decreasing with ℓ).
• Electron decouples from molecular axis as n, , N ℓ increase.• The majority of electronic states of every molecule are CNP
states.
𝑟𝑚𝑖𝑛∝ ℓ (ℓ+1) ℓR
Uses for Core Nonpenetrating States
4
State selective ion generation Molecular deceleration
Molecular Ion Structure Quantum Information
Hudson, Odom Lundeen (atoms), Field
Merkt, Meijer, Lewandowski,,Ubachs, Hinds
Field
1.8455 1.846 1.8465 1.847 1.8475 1.848 1.8485 1.849 1.8495
x 104
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
Probe laser/cm-1
Inte
grat
ed F
IDStark Demolition via chirped pulse millimeter wave spectroscopy
6
CNPCP
CP or CNP
1V/cm
CNP l>4
FIDno
FID
CP32.96 33.96 35.02 36.04 37.07 38.08
33.3733.67
35.24 36.58
• Different field intensities can discriminate between quantum defects.
The Zone of Death
7
ABAB
+
hν
e- (n ≈ 30)
A B+
AB+
e-
R
Energy
R
Energy
A+ + B-
A + B
• Core nonpenetrating states are both scientifically interesting and protect themselves from nonradiative decay.
• Difficult to access with many photons when fighting fast decay processes.
• Can access nearly nonpenetrating states with laser through perturbations located near integer n*, and/or at high N when ℓ uncoupling becomes strong.
Simple ways to deal with the Zone of Death
8
generator
detector
TOF
LIF
pump lasers
5% NO in He
• Transitions to higher- ℓstates observed in ion channel
• No FID yet detected in the general expansion (needs ~1 μs)
• May require pulse sequence to excite to even higher ℓ
Avoiding the Zone of Death altogether
9
τ <1ns
τ >1µs
τ ~100ns
(f) State
h Stateg State
(d) State τ ~100 ns
• STImulated Rapid Adiabatic Passage (STIRAP) is a three state, two photon coherent population transfer technique.
• Capable of full population transfer.
• Intermediate state never populated.
• Robust against changes in experimental conditions.
ωL
ωmm
Ɛmm ƐL
Technological Hurdles
10
Modifiable chirp shape
Short time phase
stability
Tunable chirp rate
Long time phase
stability
• Similar requirements for the laser – current plan is to pulse amplify a CW laser for phase stability, with a 100 ns pump laser if possible
Conclusions• Core nonpenetrating states are a fertile ground
for future experiments in a variety of fields.• Access to high-ℓ states demonstrated in Ca
through ladder climbing.• Determination of core nonpenetrating states in
BaF demonstrated through Stark Demolition measurements.
• More general techniques, in particular STIRAP, are needed for access to core nonpenetrating states in other molecules.
• Our CPmmW system is ideally suited to both identify and access (via STIRAP) core nonpenetrating states.
11
Acknowledgements• Prof. Robert Field
• Yan Zhou• Tim Barnum• Dr. Steve Coy• Ethan Klein• Dr. Tony Colombo• Dr. Jeff Kay• Dr. Carrie
Womack• Barratt Park• Jun Jiang• Dr. Josh Baraban• Bryan Changala
12
• Prof. John Doyle• Dr. Dave
Patterson
• Prof. Dave DeMille• Dr. John Berry
• Prof. Brooks Pate• Dr. Justin Neill
• Prof. John Muenter
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