Experiments with ultracold RbCs molecules Peter Molony Cs Rb

Peter Molony - YAO The RbCs team: Peter Molony, Phil Gregory, Michael Koeppinger, Zhonghua Ji, Bo Lu and Simon Cornish (PI) Theory:Caroline Blackley, Ruth Le Sueur, Jeremy Hutson

Peter Molony - YAO Goal: A quantum array of polar molecules Mott Insulator Transition Convert to ground state RbCs molecules Jaksch et al., PRL 89, (2002) Damski et al. PRL 90, (2003) Rubidium Caesium RbCs: Stable against reactive collisions d = 1.25 D, B rot = 0.5 GHz Induced d eff = d / 3 for E = B rot / d = 0.8 kV / cm

Peter Molony - YAO The experiment Dipole trap loaded by reducing field gradient Atoms collected in MOT Evaporation in quadrupole trap Load quadrupole trap Levitated dipole trap Apply a magnetic gradient to tilt the trap Reduce the beam intensity to lower the trap depth RF 2-species BEC! Phys. Rev. A (2013)

Peter Molony - YAO The experiment 1.Create a high phase space density atomic sample. 6S 1/2 X1+X1+ a3+a3+ (1) 3  Deeply Bound Molecule Feshbach Molecule Free Atoms ~1560nm ~980nm Magneto-association Stimulated Raman Adiabatic Passage 2. Associate weakly-bound molecules via a Feshbach resonance. 3. Transfer Feshbach molecules to the rovibrational ground state using stimulated Raman adiabatic passage (STIRAP). Potential Energy Convert atoms to molecules Atomic State Molecular Bound State Magnetic Field (B)

Peter Molony - YAO RbCs trapping ~4000 optically trapped molecules Phys. Rev. A (2014) Cs Rb

Peter Molony - YAO RbCs STIRAP L.P. Yatsenko et al., PRA 65, (2002) SS PP   SS PP  1  2 3 Relative linewidth of the two lasers D

Peter Molony - YAO RbCs STIRAP L.P. Yatsenko et al., PRA 65, (2002) Narrow linewidth High intensity Intensity control

Peter Molony - YAO RbCs spectroscopy Figure: M. Debatin, PhD Thesis, Innsbruck (2013) Data:S. Kotochigova and E. Tiesinga, J. Chem. Phys. 123, (2005) O. Docenko et al., PRA 81, (2010) STIRAP:W.C. Stwalley, EPJD 31, (2004) Excited state with mixed singlet – triplet character Good Franck–Condon overlap for both transitions Our laser: 6330 → 6711 cm -1 Find suitable intermediate state

Peter Molony - YAO RbCs STIRAP optical setup 1556 nm 980 nm EOM 980 nm DL Pro Cavity Wavemeter Experiment EOM 1556 nm DL Pro Fibre Coupler /2 Waveplate /4 Waveplate Optical Isolator Polarising Beam Splitter Glan-Thompson Polariser AOM Shutter Dichroic Mirror Photo Diode Molecules 1556 nm 980 nm

Peter Molony - YAO RbCs STIRAP optical setup

Peter Molony - YAO RbCs spectroscopy 7 transitions found so far:v’=38J’= (2) GHz v’=38J’= (2) v’=37J’= (2) v’=35J’= (2) v’=29J’= (2) v’=29J’= (2) v’=29J’= (2)

Peter Molony - YAO Ground state spectroscopy

Peter Molony - YAO Ground state rotational constant B rot = (1) cm -1 = (4) MHz Theory= 0.016(3)J Phys Chem A 116,11101 (2012) v=1 state 50 cm -1 higher

Peter Molony - YAO Outlook RbCs molecules in optical dipole trap. Magnetic moment of 87 RbCs in different internal states measured. Spectroscopy on electronically excited states. Absolute ground state found by spectroscopy. Setup ready for STIRAP. Summary Cs Rb

Peter Molony - YAO Outlook Measure dipole moment of ground state 87 RbCs molecules (electrodes ready) Transfer molecules into absolute ground state (STIRAP) Produce 85 RbCs molecules in new dipole trap New experimental setup Outlook Phys. Rev. A (R) (2013)

Peter Molony - YAO Goal: A quantum array of polar molecules Mott Insulator Transition Miscible Immiscible Convert to ground state RbCs molecules U 12 < (U 11 + U 22 )/2U 12 > (U 11 + U 22 )/2 Jaksch et al., PRL 89, (2002) Damski et al. PRL 90, (2003) Rubidium Caesium RbCs: Stable against reactive collisions d = 1.25 D, B rot = 0.5 GHz Induced d eff = d / 3 for E = B rot / d = 0.8 kV / cm

Peter Molony - YAO Last time Cs 2 Feshbach molecules

Peter Molony - YAO Last time

Peter Molony - YAO Last time

Peter Molony - YAO Last time

Peter Molony - YAO Last time

Peter Molony - YAO Magnetic moment

Peter Molony - YAO Magnetic moment

Peter Molony - YAO Trapped Cs 2 molecules

Peter Molony - YAO RbCs Feshbach molecules

Peter Molony - YAO RbCs Feshbach Molecules Cs Rb ~5000 RbCs molecules

Peter Molony - YAO RbCs molecules Magnetic moment measurement Keep molecules in the same position since the magnetic moment changes while the molecules are falling Vary magnetic field gradient Measure position after different period of time  mol,181G = -0.84(1)  B

Peter Molony - YAO RbCs magnetic moment

Peter Molony - YAO Next step RbCs excited state spectroscopy Excited state potential through Fourier transform spectroscopy (FTS) (O. Docenko et al., PRA 81, (2010)) Ground state potential measured using laser-induced fluorescence combined with Fourier transform spectroscopy (LIF-FTS) (C.E. Fellows et al., J. Mol. Spectrosc. 197, 19 (1999))

Peter Molony - YAO Next step RbCs excited state spectroscopy M. Debatin et al., Phys. Chem. Chem. Phys. 13, (2011) Resonances at ~ 1556 nm  FWHM ~ 2  x 5 MHz

Peter Molony - YAO First identify a suitable intermediate state with sufficient oscillator strength with both connected levels Excited state potential from PRA 81, (2010) Ground state potential from J. Mol. Spectrosc. 197, 19 (1999) Single photon excited state spectroscopy: Irradiate molecules only with L1 for 10  s to 10 ms Gamma can be calculated detuning the laser Rabi frequencies can be calculated using the decay during irradiation Two photon dark state resonance spectroscopy: Simultaneous irradiation with rectangular light pulses of L1 and L2 10 – 100  s irradiation time  L2 <<  L1 (more 980 nm light) Vary detuning of L1 (1550 nm) and keep L2 in resonance How do I know  L2 = 0 ???