New emission Mössbauer spectroscopy studies at ISOLDE in

2015Haraldur Páll Gunnlaugsson, Torben E. Mølholt,

Karl Johnston, Juliana Schell, The Mössbauer collaboration at ISOLDE CERN, The ISOLDE

collabroation

2

Outline

Brief introduction to emission Mössbauer spectroscopyNew beam, why, how, what ... 119In (→119Sn) laser ionized 151Dy (→152Eu) 197Hg (→119Au) 119Ag (→119Sn) laser ionized

Conclusions/Outlook

3

eMS

Mössbauer Spectroscopy (MS)- Valence/spin state- Site symmetry- Magnetic interactions- Binding properties- Relaxation phenomena- ......

Parent in sample

Mössb. State (t)

Stable daughter

ΔE ≈ neV

Daughter

Standard absorber

Detector

Emission MS (eMS)- High dilution (10-4%)- Recoils (interstitals)- Play with chemistry

v v

v

4

Important parameters

d

DEQ

Split

×

×

×

DR/R

Q‘s

g‘s

|Y(0)|2

VZZ

Bhf

-12 -8 -4 0 4 8 12

Typical spectrum and analysis Main interactions

Velocity (mm/s)

Binding properties:

0.00.10.20.30.40.50.60.70.80.91.0

0 200 400 600 800

f-fac

tor

Temperature (K)

57Fe (14.4 keV) in iron

197Au (77.3 keV) in gold

< DE = ħ/t

5

Mössbauer isotopes

H He

Li Be B C N O F Ne

Na Mg Al Si P S Cl Ar

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe

Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Pb Po At Rn

Fr Ra Ac

Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Th Pa I Np Pu Am Cm Bk Cf Es Fm Md No Lw

6

Mössbauer lab in b508March 2015

May 2015

7

119In for 119Sn eMS laser ionized

119In (2.4 m)

24 keV18 ns

119Sn

Laser ionization → 20 times higher yieldSpectra measured in few minutes instead of tenths of minutes

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Example: GaxMn magnetic alloys

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

9

Mn/Fe results

Broadened lines due to unresolved magnetic interactionsµFe:GaxMn ~ 0.4 µB/Fe (a-Fe = 2.2 µB/Fe)

-10 -5 0 5 10

Emis

sion

(arb

. uni

ts)

Velocity (mm/s)

57Mn at 300 K

GaxMn

a-Fe

10

In/Sn results

Broad hyperfine field distributionµSn:GaxMn ~ 4 µB/Sn 10 times higher than Mn µSn:GaxMn, Max ~ 8 µB/Sn

World record?Effect spread out : Took ~20 minutes to

measure Would have taken 8

hours without lasers-30 -20 -10 0 10 20 30

Emis

sion

(arb

. uni

ts)

Velocity (mm/s)

119In at 300 K in GaxMn

57Mn at 300 K in GaxMn(as before)

100%

5%

11

151Eu

”nice” 21.54 keV resonanceFed by 151Gd (120 d)Well sensitive to charge state density: easy distinction between Eu2+ and Eu3+

Good magnetic probeNot very sensitive to quadrupole interactions

RE are very interesting as doping in semiconductorsUsed to manipulate the optical properties of the host for fx. non-liniear optical processes

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151Gd productio at ISOLDE

Implantation (~10 minutes) of 151Dy + 30% 135XO~4% decay to 147GdAfter ~2 weeks, sources ready for eMS measurementsat RT

149Dy4.2 m

150Dy7.2 m

151Dy17.6 m

152Dy2.4 h

153Dy6.4 h

154Dy3E6 y

148Tb60 m

149Tb4.1 h

150Tb3.48 h

151Tb17.6 h

152Tb17.5 h

153Tb2.34 d

147Gd38 h

148Gd71 y

149Gd9.3 d

150Gd1.8E6 y

151Gd124 d

152Gd0.2%

146Eu4.6 d

147Ey24.1 d

148Eu54.5 d

149Ey93 d

150Eu37 y

151Eu48%

145Sm340 d

146Sm10E7 y

147Sm15 %

148Sm11.2%

149Sm13.8%

150Sm7.4%

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Setup and results

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Preliminary results

~5-10 minutes to prepeare each sample~15 metal samples implanted to investigate isomer-shift vs. electronic configurationMeasurements on-going

-20 -10 0 10 20

Rel

ativ

e tra

nsm

issi

on (a

rb. u

nits

)

Velocity (mm/s)

151Gd (→151Eu) in Copper at RT

As implanted

Annealed at 350 � C

Eu3+S

Eu3+D

Eu2+D

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197Au Mössbauer state

Can be fed from Pt and HgHuge interest in Hg in biochemistryE0 = 77.34 keV requires both source and absorber at cryogenic temperatures

Compounds of gold

Litterature:Much is known about (bio)chemistry of goldAdditionally, we would better determine binding properties (qD’s)qD coordination

16

d

DEQ

17

Experimental setup

Hg produced from spallation in a molten Pb target197Hg/199Hg (PAC) implanted into iceBiomolicules prepeared and sample frozenAbsorber & moving source at low temperatures

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ResultsAu Used for calibration,

position (≡ 0.0 mm/s) effect (qD = 170 K)

Ta Isomer-shift: 5.7(2) mm/s

Literature 5.8 mm/s qD (Au in Ta): 235(10) K

MDA: 230 K

-12 -8 -4 0 4 8 12

Rel

ativ

e tra

nsm

issi

on

Velocity (mm/s)

~5î 1011 197HgMeasured at 77 K

1% Au

Ta

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Conclusions/outlook

More Mössbauer isotopes more physicsEach MS isotope comes with new tasks, which can be overcome

2015

>2015

20

Acknowledgements

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 membersNew members 2014

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119Ag for 119Sn eMS

Allows to study interstitial defects?Cadmium of considerable interest in semiconductors Difficult chemistry of Cd Comparison to 111Cd PAC data Comparison to 119In MS data

(no significant recoil)

119In (2.4 m)

24 keV18 ns

119Sn

119Cd (2.2 m)

119Ag (2 s)High energy beta~60 eV recoil

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Very limited results

We also count the high energy betasTricks have to be applied to measure good spectra

0

50

100

150

200

250

300

600 1100 1600 2100 2600

Cou

ntra

te (s

-1)

Time (s)

Implantation

~2 s decay Cd/In

decay

Spectrum obtained in silicon dominated by substitutional Sn