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Graham Lochead01/02/10
Autoionization of strontium Rydberg states
Graham Lochead01/02/10
Outline
• Autoionization/experimental overview
• Low n results
• High n results
Graham Lochead01/02/10
Autoionization
5s2 5s5p 5sns(d) 5pns(d) 5s1/2
461 nmprobe
413/420 nmcoupling
408 nmautoionization
4 μs overlappedcounterpropagating CW10 ns pulse
Prepare atomsin ground state
Graham Lochead01/02/10
Data acquisition
Step the Rydberg coupling laser over the transition
Collect and integrate the ion signal at each wavelength
Fit a Gaussian to the lineshape
Extract height and normalise by atom number/pulse energy where appropriate
Graham Lochead01/02/10
Error analysis
Analysis not yet completed
Major sources of error:• Atom number fluctuation• Shot-to-shot fluctuation of the pulse laser power
Initial estimates of signal error < 15%
Graham Lochead01/02/10
20S Rydberg state lifetime
Graham Lochead01/02/10
20S autoionizing spectrum
Graham Lochead01/02/10
19D Rydberg state lifetime
Graham Lochead01/02/10
19D Rydberg state lifetime
Lifetime previously measured to be 740 ± 40 ns
Grafström et. al, PRA 27, 947 (1983)
Graham Lochead01/02/10
19D autoionizing spcetrum
Shape due to quantum defect difference
Cooke et. al, PRL 40, 178 (1977)
Graham Lochead01/02/10
Total Rydberg ionization
• Were able to completely ionize Rydbergs
• Loss fraction calculated – total Rydberg number
• Can calculate Rydberg-Rydberg ionization
Graham Lochead01/02/10
56D lifetime measurements
413 power (mW) Lifetime (μs)
5 16.3 ± 0.9
10 80 ± 6
15 98 ± 5
20 109 ± 19
Dutta et. al, PRL 86, 3993 (2001)
Possibly caused by high angular momentum state mixing
Graham Lochead01/02/10
56D autoionizing spectrum
Graham Lochead01/02/10
56D density effects
Graham Lochead01/02/10
Outlook
• Finish error analysis
• Follow up experiments without pulse laser
• Explain the 56D data
