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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
8
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
12
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%
13
Setup and results
14
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
15
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
18
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
19
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
21
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
22
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