Funded by: NSF Timothy C. Steimle, Fang Wang a Arizona State University, USA & Joe Smallman b, Physics Imperial College, London a Currently at JILA THE [18.1], [18.6] and [18.7] EXCITED STATES OF YTTERBIUM FLUORIDE, YbF b Visitor June 2013 This is a work in progress!

Goal: Gain a better understanding of excited states of YbF Motivation: laser cooled fountain to enhance eEDM measurement by Hind’s group: As initial step we have measured the fluorescence branching ratio: “Design for a fountain of YbF molecules to measure the eEDM” Tarbutt, Sauer, Hudson and Hinds New Journal of Physics, 15, (2013) [18.6]  =1/2 [18.7]  =1/2 [19.1]  =1/2 [19.3]  =1/2 [18.1]  =1/2 X 2  + (v=0) X 2  + (v=2) X 2  + (v=1) X 2  + (v=3) Cooling cycle Re-populating Information about these state is useful in designing experiment “Radiative branching ratio for excited states of 174 YbF: application to laser cooling” Smallman, Wang, Tarbutt & Hinds; J. Mol. Spectrosc. (June 2014). A 2  1/2 (v=0)

1.Barrow & Chojnicki “ Analysis of Optical …” J. Mol Spec. (1975) 2.Lee & Zare “ Chemiluminescence of YbCl & YbF“ J. Mol Spec. (1977) 3.Dunfield et al (New Brunswick group) “ Laser Spectroscopy…” J. Mol Spec. (1995). Previous Optical Spectroscopic Studies YbF Ed Hind’s Group (beam measurements) 1.Sauer et al “Anomalous spin-rotation coupling in the X 2  +...” PRL (1995) 2.Sauer, et al “Laser-rf double resonance of 174 YbF in the X 2  + state: Spin- rotation, hyperfine interactions, and the electric dipole moment.” JCP (1996). 3.Sauer,et al “ Perturbed hyperfine doubling in the A 2  ½...” JCP (1999) 4.Tarbutt,et al “ A jet beam source of cold YbF radicals.” J Phys. B (2002) 5.Hudson, et al. “Measurement of the Electron Electric Dipole Moment Using YbF Molecules.” Phys. Rev.Lett. (2002), 6.Condylis et al “Stark shift of the A 2  1/2 state in 174 YbF ”. JCP (2005) “ Our measurements indicate that the lower lying of these two states is predominately of [18.6]0.5 (v=0) character and not A 2  1/2 (v=1) and previously thought 1.” [18.6]  =1/2 [18.7]  =1/2 Do either of these two look resemble the [18.1] (A 2  1/2 (v=1)) state ? A 2  1/2 (v=1) ? Colin Linton and Allan Adam Doppler limited study of [18.1], [18.6], [18.7] [19.1], [19.3]-X 2  + bands of a hot sample.

Work present here and previous : Radiative lifetimes High-resolution excitation Optical Stark Optical Zeeman Dispersed LIF [18.6] [18.1] [18.7] [19.1] [19.3] Ref.2 2) “Radiative branching ratio for excited states of 174 YbF: application to laser cooling” Smallman, Wang, Tarbutt & Hinds; J. Mol. Spectrosc. (2014). Ref.2 Ref.1 1) “FCF & lifetimes for the A 2  1/2 –X 2  + transitions of 174 YbF” Zhaung et al. PCCP 13, ,(2011). Ref.1 Ref. 3 3) “ The hyperfine interactions in the A 2  1/2 and X 2  + states of YbF” Steimle, Ma and Linton, JCP (2007). Ref. 4 4) “Stark shifts on the A 2  1/2 state of 174 YbF” Hind’s group, JCP (2005) Ref. 5 5) “Opt. Zeeman Spectroscopy of YbF”, Ma, et al JPCA 113, (2009). Here

Well collimated molecular beam Rot.Temp.<10 K Single freq. or pulsed tunable laser radiation Stark plates Optical Stark spectroscopy Metal target Pulse valve skimmer Ablation laser Reagent & Carrier Mol. Beam spectrometer Rare earth magnets Optical Zeeman Spectroscopy PMT Gated photon counter LIF

Magnetic field and molecular beam reaction CW dye laser: ~520nm Molecular beam Focus areas Rare earth magnets  5000 Gauss

Low-resolution LIF with Pulsed Dye laser of [18.1]-X 2  + At low-resolution, the, [18.1]-X 2  + [18.6]-X 2  + and [18.7]-X 2  + bands look very similar.

-1- NucleusIsotopeNatural Abundance (%) Spin(h/2  ) Magnetic moment (  N ) Elect. quadrupole moment( cm 2 ) Yb / / F100.01/ Nuclear Properties for Yb and F Many Isotopologues !

High resolution [18.6]-X 2  + near P 1 (N)+ P Q 12 (N) band head 176 YbF Band Head 174 YbF Band Head X10 O P 12 (2) 174 YbF 176 YbF 172 YbF 170 YbF 173 YbF 171 YbF Predicted 174 YbF O P 12 (2) observed

Analysis of 174 YbF [18.6]-X 2  + high-resolution, field- free spectrum: X 2  + (v=0) All parameters held fixed to FTMW values Dickinson, et al. J. Chem. Phys. 155 (2001) 6979–6989. [18.6] treated as  =1/2 of 2  A, &A D held fixed Dunfield et al values. Lst. sq. fit to transition wave numbers Large variation between [18.6] and [18.1] states! New Brunswick group

X 2   : Case b  S with two nuclear spin 173 Yb(I=5/2)F G = 2 & Yb(I=1/2)F G = 0 & 1 [18.1] (A 2  v =0  : and [18.2] Case a  J with two nuclear spin 173 Yb(I=5/2)F F 1 = J-5/2.. J+5/2; F=F 1  1/2 171 Yb(I=1/2)F F 1 = J-1/2.. J+1/2; F=F 1  1/2 Hyperfine in odd isotopes:

180 MHz Comparison of 171 Yb(I=1/2) hyperfine in O P 12 (3) lines [18.6] O P 12 (3) lines cm YbF [18.2] O P 12 (3) lines cm YbF 560 MHz X 2  + (v=0) [18.6] or [18.1] [18.2] and [18.1] states have very different 171 Yb hyperfine! Complete analysis of 171 Yb(I=1/2) and 173 Yb(I=5/2) is in progress !

Spectra [18.6] o P 12 (2) Comparison of Zeeman effect in [18.1] and [18.6] o P 12 (2) transition Energy levels II I a h Par[18.1][18.6] glgl 00 gsgs 2.00 gLgL 1.00 gl’gl’ Large variation due to proximity of “perturbing” state Six parameters required: X 2  + : g s and g l A 2  g L, g s g l  and g’ l Constrained to ESR (Weltner et al.) values

[19.2] Time (ns) LIF signal  =148.8 ns Comparison of fluorescent lifetimes [18.1], [18.6],[18.7], [19.1]& [19.2], [19.1]  =30.2 ns LIF signal Time (ns) [18.1][18.6][18.7][19.1][19.3]  (ns) Very similar Very different

Comparison of permanent electric dipole moments [18.1] and [18.6] o P 12 (2) transition [18.1][18.6][18.7][19.1][19.2]  (D) 2.38(8)2.35 A o P 12 (2) X 2   (v=0,1) F=  32 matrix Eigenvalues for X 2   (v=0) A 2  (v=0) F=  64 matrix Eigenvalues for A 2  (v=0) Least Sq. fitting. precisely measured Stark shifts A) Measured but not yet analyzed Hind’s group, JCP (2005) : 2.48(3) D

Summary We are making good progress on determining the character of the excited states of YbF. Thank you ! [18.6]  =1/2 [18.7]  =1/2 The based upon the lifetimes, the [18.6] and [18.7] states seem to be completely mixed. Special thanks to Profs. Colan Linton and Allan Adam