Direct Observation of Rydberg Rydberg Transitions in Calcium

Direct Observation of Rydberg –Rydberg Transitions in Calcium Atoms K. Kuyanov-Prozument, A. P. Colombo, Y. Zhou, G. B. Park, V. S. Petrović, and R. W. Field Department of Chemistry Massachusetts Institute of Technology The Ohio State University International Symposium on Molecular Spectroscopy 22 June 2010

What I mean by “direct” We extended Brooks Pate’s CP-FTMW to mmwaves. p Adapt CPmm. W for Rydberg–Rydberg transitions: p Polarize with (chirped, broadband) mmwaves. p Detect the free induction decay. p

Challenges for Rydberg–Rydberg Transitions Δn* ≈ 1 has transition dipole moments ~5, 000 Debye at n* = 30 – 40. p ~100 p. W over 1 cm 2 will saturate a transition in 1 μs. p (We have 30 m. W. ) p Collective effects preclude high number density. p We enlarged the volume of the interaction region. p

Exciting Calcium Atoms |Δn*| < 1 n* ≈ 30 – 40 70 – 84 GHz 1 P° or 1 F° 1 S or 1 D initial Rydberg state 800 nm ~ 12, 500 cm− 1 1 P° 3 p 64 s 5 p intermediate state 272 nm 3 p 64 s 2 ~ 2. 5 cm− 1 36, 700 cm− 1 1 S ground state

Pulse Timings Gunn Oscillator Gas pulse Gunn Lock Box Ablation laser pulse 12 GHz Scope 10 MHz Standard mm-wave Chamber (top view) 10. 7 GHz PDRO mm-wave OR Chamber Dye laser pulses Ionization Chamber Dye laser pulses mm-wave pulse Extraction pulse Ionization Chamber (top view) Ionization Chamber (side view) 1 GHz Scope MCP 3. 96 GHz PDRO Einsel tube 4. 2 GS/s AWG x 2 x 4 1200 V 1500 V + Extraction pulse Variable Attenuator Delay Generator A Gas Nozzle Driver Spatial Filter Delay Generator B Spatial Filter Extraction Pulse Ablation YAG Laser Dye Laser x 2 Dye Laser Excitation YAG Laser

A Signal in the Time Domain

Signals in the Frequency Domain 34. 13 p 33. 67 s 41. 73 d 40. 88 f 30. 12 p 29. 80 d 37. 78 d 37. 13 p Observed lines (41. 73 d– 40. 88 f excluded) agree with Gentile et al. , Phys. Rev. A 42, 440 (1990).

FID Within a Chirp

Photon Echo 10 ns, 6 V/m π/2 2. 2 μs 20 ns, 6 V/m π 2. 2 μs Time/μs

Molecules Goal: “Pure Electronic Spectroscopy” on core-nonpenetrating states. p Characterize multipole moments and polarizabilities of ion core. p p CPmm. W spectroscopy has the n n Resolution we need (103 times better than pulsed dye lasers). Survey capability we like.

Acknowledgments Brooks Pate p Justin Neill p Adam Steeves p p NSF, DHS, DOE p Tektronix

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The Problem(s) with Molecules p Fast predissociation (and autoionization) p Complementary approaches n Populate high-ℓ states Coherent, multiphoton excitations p Stark mixing p n Separate chirp from FID p Polarization spectroscopy

Advantages of Large Transition Dipole Moments Can polarize a transition in ~10 ns. p No penalty for using full oscilloscope bandwidth (10 GHz), with resolution better than 1 MHz. p More of the (most intense) FID. p Exploit fast/strong polarization. p

Rabi Oscillations π/2 Time/μs π Time/μs 3π/2 Time/μs 2π Time/μs

Which way is up? Time/μs 34. 13 p 33. 67 s Time/ns 41. 73 d 40. 88 f

Pulse Timings Gunn Oscillator Gas pulse Gunn Lock Box Ablation laser pulse 12 GHz Scope 10 MHz Standard mm-wave Chamber (top view) 10. 7 GHz PDRO mm-wave OR Chamber Dye laser pulses Ionization Chamber Dye laser pulses mm-wave pulse Extraction pulse Ionization Chamber (top view) Ionization Chamber (side view) 1 GHz Scope MCP 3. 96 GHz PDRO Einsel tube 4. 2 GS/s AWG x 2 x 4 1200 V 1500 V + Extraction pulse Variable Attenuator Delay Generator A Gas Nozzle Driver Spatial Filter Delay Generator B Spatial Filter Extraction Pulse Ablation YAG Laser Dye Laser x 2 Dye Laser Excitation YAG Laser

Time Series of Echos

Phase-Lock Loop for Gunn Oscillator Directional Coupler Variable Attenuator Difference Freq. Lock Box Subharmonic mixer Diplexer 10 MHz Rb Clock PDRO ~2− 18 GHz (or synthesizer) Out to mixer