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Rapid Light Manipulation Techniques for Collinear Laser Spectroscopy and their Application for Neutron-Deficient Francium

Annika Voss

University of Jyväskylä Finland

European Nuclear Physics Conference 2015 Groningen, NL

e Nuclear Laser Spectroscopic Landscape

Status as of July 20th, 2015

Z=40 Z=28 Z=82 Z=50 Z=20 N=20 N=28 N=40 N=50 N=82 N=126 N=152

Stable isotopes Published data Unpublished data

Annika Voss Light Manipulation & n-def. Francium EuNPC 2015

Nuclear Properties from Atomic Spectra

I = 0 Isotope 1

Counts

I = 0 Isotope 2

Relative Frequency [MHz]

I > 1/2 Isotope 3 Centroid

Isotope Shis → Changes in RMS charge radii δ⟨r2⟩ δ⟨r2⟩A,A′ ≈ δ⟨r2⟩A,A′

sph +⟨r2⟩A′ sph · 5

4πδ⟨β2

2⟩A,A′

Hyperfine Structures Nuclear spin I Magnetic dipole moment Electric quadrupole moment QS Q Z r

sph

r dynamic deformation Q static deformation

Annika Voss Light Manipulation & n-def. Francium EuNPC 2015

Nuclear Properties from Atomic Spectra

I = 0 Isotope 1

Counts

I = 0 Isotope 2

Relative Frequency [MHz]

I > 1/2 Isotope 3 Centroid

Isotope Shis → Changes in RMS charge radii δ⟨r2⟩ δ⟨r2⟩A,A′ ≈ δ⟨r2⟩A,A′

sph +⟨r2⟩A′ sph · 5

4πδ⟨β2

2⟩A,A′

Hyperfine Structures → Nuclear spin I → Magnetic dipole moment µ → Electric quadrupole moment QS Q0 ≈ 5Z⟨r2⟩sph √ 5π ⟨β2⟩ (1 + 0.36⟨β2⟩) r dynamic deformation Q static deformation

Annika Voss Light Manipulation & n-def. Francium EuNPC 2015

Nuclear Properties from Atomic Spectra

I = 0 Isotope 1

Counts

I = 0 Isotope 2

Relative Frequency [MHz]

I > 1/2 Isotope 3 Centroid

Isotope Shis → Changes in RMS charge radii δ⟨r2⟩ δ⟨r2⟩A,A′ ≈ δ⟨r2⟩A,A′

sph +⟨r2⟩A′ sph · 5

4πδ⟨β2

2⟩A,A′

Hyperfine Structures → Nuclear spin I → Magnetic dipole moment µ → Electric quadrupole moment QS Q0 ≈ 5Z⟨r2⟩sph √ 5π ⟨β2⟩ (1 + 0.36⟨β2⟩) δ⟨r2⟩ → ⟨β2

2⟩ dynamic deformation

Q0 → ⟨β2⟩ static deformation

Annika Voss Light Manipulation & n-def. Francium EuNPC 2015

Hyperfine Pumping

Spins: I nuclear J electronic F total; ⃗ F =⃗ I +⃗ J Selection Rules: ∆J = 0, ±1; J = 0✟ ✟ ❍ ❍ →J′ = 0 ∆F = 0, ±1; F = 0✟ ✟ ❍ ❍ →F′ = 0

F = 15/2 13/2 7 2S1/2 F ′ = 17/2 15/2 13/2 11/2 7 2P3/2

SJ,J′ 100 55.3 22.5 A B C

.

Relative intensities of individual HFS transitions:

. SF,F′ = (2F + 1)(2F′ + 1) {F F′ 1 J′ J I }2 SJ,J′,

208Fr

I = 7 high-spin multiplet

Annika Voss Light Manipulation & n-def. Francium EuNPC 2015

e Laser Spectroscopy Beamline @ T

RFQ

Annika Voss Light Manipulation & n-def. Francium EuNPC 2015

Collinear Laser System

for Intensity Modulation and Fast Frequency Switching Focus & Power Adjustment, Beamline Injection Frequency Stabilisation Frequency Switching Intensity Modulation

λ/2 ν-AOM λ/4 f1 f2 φ-EOM 100m Fibre Link (single-mode) M2 SolsTiS Lighthouse SPROUT λ-meter Photodiode Fabry-Pérot Etalon Interference Filter Faraday Isolator HeNe IRIS Movable Mirror Beam Profiler 7m to Beamline 300MHz Blocked Path Monitor ν-EOM Annika Voss Light Manipulation & n-def. Francium EuNPC 2015

High-Frequency Intensity Modulation

Voss et al., 2013, PRL 111, 122501

+ + ++ + + + + + +

+

• photomultiplier

tube to data aquisition system uorescence photons counter-propagating laser beam acceleration electrodes

+

• +

+ + +

• oo
• continuous photon stream

charge exchange cell hot alkali vapour ~40 cm

• r ~3 µs at E = 20 keV

. 7s 2S1/2 . 7p 2P3/2

−24500 −24000 −23500 −23000 −22500 −22000 −21500

Frequency with respect to 208Fr centroid [MHz]

20 40 60 80 100 120 140

Normalised count rate

continuous

Voss et al., 2013, Phys. Rev. Le. 111, 122501

2 4 6 8 10

Photon Scatters

10−4 10−3 10−2 10−1 100 101 102 103

Expected Intensity [%]

Transitions A & F Transition B Transition C Transition D Transition E

Annika Voss Light Manipulation & n-def. Francium EuNPC 2015

High-Frequency Intensity Modulation

Voss et al., 2013, PRL 111, 122501

+ + ++ + + + + + +

+

• photomultiplier

tube to data aquisition system uorescence photons counter-propagating laser beam acceleration electrodes

+

• +

+ + +

• oo
• photon pulse-train

charge exchange cell hot alkali vapour ~40 cm

• r ~3 µs at E = 20 keV

. 7s 2S1/2 . 7p 2P3/2

−24500 −24000 −23500 −23000 −22500 −22000 −21500

Frequency with respect to 208Fr centroid [MHz]

20 40 60 80 100 120 140

Normalised count rate

modulated continuous

Voss et al., 2013, Phys. Rev. Le. 111, 122501

2 4 6 8 10

Photon Scatters

10−4 10−3 10−2 10−1 100 101 102 103

Expected Intensity [%]

Transitions A & F Transition B Transition C Transition D Transition E

Annika Voss Light Manipulation & n-def. Francium EuNPC 2015

Rapid Frequency Switching

Voss et al., 2015, PRC 91, 044307

+ + ++ + + + + + +

+

• photomultiplier

tube to data aquisition system fluorescence photons counter-propagating laser beam acceleration electrodes

+

• +

+ + +

• oo
• photon pulse-train

charge exchange cell hot alkali vapour

ν-AOM λ/4 f1 f2 IRIS

20 40 60 80 100 120 140 160

Counts per 5ns

RF1, 90MHz RF2, 100MHz RF3, 110MHz 2 4 6 8 10

Time [µs]

20 40 60 80 100 120 140

Voss et al., 2015, Phys. Rev. C 91, 044307 Annika Voss Light Manipulation & n-def. Francium EuNPC 2015

Rapid Frequency Switching

Voss et al., 2015, PRC 91, 044307

+ + ++ + + + + + +

+

• photomultiplier

tube to data aquisition system fluorescence photons counter-propagating laser beam acceleration electrodes

+

• +

+ + +

• oo
• photon pulse-train

charge exchange cell hot alkali vapour

ν-AOM λ/4 f1 f2 IRIS

20 40 60 80 100 120 140 160

Counts per 5ns

RF1, 90MHz RF2, 100MHz RF3, 110MHz 2 4 6 8 10

Time [µs]

20 40 60 80 100 120 140 0.0 0.2 0.4 0.6 0.0 0.2 0.4 0.6

Count Rate

−22800 −22700 −22600 −22500 −22400

Relative Frequency [MHz]

0.0 0.2 0.4 0.6

νRF1 νRF2 νRF3

Voss et al., 2015, Phys. Rev. C 91, 044307 Annika Voss Light Manipulation & n-def. Francium EuNPC 2015

Fluorescence Spectra of 204,205,206Fr

5 10 15 0.5 1.0 1.5 2.0 m1 g m2 m2 g&m1 0.4 0.8 1.2 −24000−22000−20000−18000−16000 0.4 0.8 1.2 m1 g −12000 −11000 −10000 −9000 m2 13000 14000 15000 m2 24000 26000 28000 30000 g&m1

Count Rate

208Fr 206Fr 205Fr 204Fr

Relative Frequency [MHz] Voss et al., 2015, Phys. Rev. C 91, 044307

. . ⇒ First direct and unique spin determinations: Mass gs m1 m2 206 3 7 10 205 9/2 204 3 7 10

Annika Voss Light Manipulation & n-def. Francium EuNPC 2015

g-factors

116 118 120 122 124 126

N

0.0 0.5 1.0 1.5 2.0

g-factor

I=3 I=3 I=7 I=7 I=10 I=10

Coc Triumf

Voss et al., 2013, Phys. Rev. Le. 111, 122501 & 2015, Phys. Rev. C 91, 044307 Coc et al.,1985, Phys. Le. B. 163, 66

[(π1h9/2) ⊗ (ν3p3/2)]3 [(π1h9/2) ⊗ (ν3p1/2)]5 [(π1h9/2)]9/2 [(π1h9/2) ⊗ (ν2f5/2)]7 [(π1h9/2) ⊗ (ν1i13/2)]10

gemp corresponding to

Annika Voss Light Manipulation & n-def. Francium EuNPC 2015

Changes in MS Charge Radii

−0.5 −0.4 −0.3 −0.2 −0.1 0.0

δr2N,126 [fm2]

|β2| = 0.20 0.15 0.10 0.00 a) Pb gs Fr gs Fr m1 Fr m2 116 118 120 122 124 126

N

−0.02 −0.01 0.00 0.01

∆ [fm2]

b) Voss et al., 2013, Phys. Rev. Le. 111, 122501 & 2015, Phys. Rev. C 91, 044307 Coc et al.,1985, Phys. Le. B. 163, 66 (re-evaluated) Annika Voss Light Manipulation & n-def. Francium EuNPC 2015

Summary

• developed fast-frequency intensity modulation for collinear laser

spectroscopy

• successfully demonstrated suppression of hyperfine pumping on

neutron-deficient Fr and neutron-rich Rb

• rapid frequency switching further enhances the technique
• coincidence methods allow the PMT signal to be disentangled for

individual analysis

• techniques may be applied at all facilities pursuing collinear laser

spectroscopy on atomic species

• first direct and model-independent nuclear spin determination for

neutron-deficient Fr isotopes and isomers

• g-factors suggest strong mixing of shell-model states for ground states
• δ⟨r2⟩ mark onset of deformation around N = 119 in Fr

Annika Voss Light Manipulation & n-def. Francium EuNPC 2015

ank you!

Collaboration: (sorted by Number of Participants)

Annika Voss Light Manipulation & n-def. Francium EuNPC 2015