New emission Mössbauer spectroscopy studies at ISOLDE in 2015 Haraldur Páll Gunnlaugsson, Torben E. Mølholt, Karl Johnston, Juliana Schell, The Mössbauer collaboration at ISOLDE CERN, The ISOLDE collabroation

Outline Brief introduction to emission Mössbauer spectroscopy New beam, why, how, what...  119 In (→ 119 Sn) laser ionized  151 Dy (→ 152 Eu)  197 Hg (→ 119 Au)  119 Ag (→ 119 Sn) laser ionized Conclusions/Outlook 2

eMS Mössbauer Spectroscopy (MS) -Valence/spin state -Site symmetry -Magnetic interactions -Binding properties -Relaxation phenomena Parent in sample Mössb. State (  ) Stable daughter ΔE ≈ neV Daughter Standard absorber Detector Emission MS (eMS) -High dilution (10 -4 %) -Recoils (interstitals) -Play with chemistry v v v

Important parameters 4   E Q Split ××××××   R/R Q‘s g‘s   V ZZ B hf Typical spectrum and analysis Main interactions Velocity (mm/s) Binding properties: 57 Fe (14.4 keV) in iron 197 Au (77.3 keV) in gold  E = ħ/ 

Mössbauer isotopes 5 HHe LiBeBCNOFNe NaMgAlSiPSClAr KCaScTiVCrMnFeCoNiCuZnGaGeAsSeBrKr RbSrYZrNbMoTcRuRhPdAgCdInSnSbTeIXe CsBaLaHfTaWReOsIrPtAuHgTlPb PoAtRn FrRaAc CePrNdPmSmEuGdTbDyHoErTmYbLu ThPaINpPuAmCmBkCfEsFmMdNoLw

Mössbauer lab in b508 6 March 2015 May 2015

119 In for 119 Sn eMS laser ionized In (2.4 m) 24 keV 18 ns 119 Sn Laser ionization → 20 times higher yield Spectra measured in few minutes instead of tenths of minutes

Example: Ga x Mn magnetic alloys When grown as thin films, these alloys show interesting magnetic properties. Used fx. for high density perpendicular magnetic recording Magnetic properties are not fully understood  57 Mn → 57 Fe : Mn sub-lattice  119 In → 119 Sn : Ga sub-lattice 8

Mn/Fe results Broadened lines due to unresolved magnetic interactions  µ Fe:GaxMn  ~ 0.4 µ B /Fe (  -Fe = 2.2 µ B /Fe) 9 57 Mn at 300 K Ga x Mn  -Fe

In/Sn results Broad hyperfine field distribution  µ Sn:GaxMn  ~ 4 µ B /Sn  10 times higher than Mn  µ Sn:GaxMn, Max ~ 8 µ B /Sn World record? Effect spread out :  Took ~20 minutes to measure  Would have taken 8 hours without lasers In at 300 K in Ga x Mn 57 Mn at 300 K in Ga x Mn (as before) 100% 5%

151 Eu ”nice” keV resonance Fed by 151 Gd (120 d) Well sensitive to charge state density: easy distinction between Eu 2+ and Eu 3+ Good magnetic probe Not very sensitive to quadrupole interactions 11 RE are very interesting as doping in semiconductors Used to manipulate the optical properties of the host for fx. non-liniear optical processes

151 Gd productio at ISOLDE Implantation (~10 minutes) of 151 Dy + 30% 135 XO ~4% decay to 147 Gd After ~2 weeks, sources ready for eMS measurementsat RT 12

Setup and results 13

Preliminary results ~5-10 minutes to prepeare each sample ~15 metal samples implanted to investigate isomer-shift vs. electronic configuration Measurements on-going 14

197 Au Mössbauer state Can be fed from Pt and Hg Huge interest in Hg in biochemistry E 0 = keV requires both source and absorber at cryogenic temperatures 15

Compounds of gold Litterature: Much is known about (bio)chemistry of gold Additionally, we would better determine binding properties (  D ’s)  D  coordination 16  EQEQ

Experimental setup Hg produced from spallation in a molten Pb target 197 Hg/ 199 Hg (PAC) implanted into ice Biomolicules prepeared and sample frozen Absorber & moving source at low temperatures 17

Results Au  Used for calibration, position (≡ 0.0 mm/s) effect (  D = 170 K) Ta  Isomer-shift: 5.7(2) mm/s Literature 5.8 mm/s   D (Au in Ta): 235(10) K MDA: 230 K 18

Conclusions/outlook More Mössbauer isotopes  more physics Each MS isotope comes with new tasks, which can be overcome >2015

Acknowledgements 20 The Mössbauer collaboration at ISOLDE/CERN, >30 active members with new members (2014) from China, Russia, Bulgaria, Austria, Spain: Four experiments (IS501, IS576, IS578, I-161) Existing members New members 2014

119 Ag for 119 Sn eMS Allows to study interstitial defects? Cadmium of considerable interest in semiconductors  Difficult chemistry of Cd  Comparison to 111 Cd PAC data  Comparison to 119 In MS data (no significant recoil) In (2.4 m) 24 keV 18 ns 119 Sn 119 Cd (2.2 m) 119 Ag (2 s) High energy beta ~60 eV recoil

Very limited results We also count the high energy betas Tricks have to be applied to measure good spectra 22 Implantation ~2 s decay Cd/In decay Spectrum obtained in silicon dominated by substitutional Sn