Measuring Xenon and Krypton in Primitive
Material
Jamie Gilmour, Ilya Strashnov, Sarah Crowther,
John Cowpe.
SEAES University of Manchester
1
Xenon and Krypton
• 
• 
• 
• 
• 
Extinct radioisotopes… 244Pu, 129I.
Nucleosynthetic signatures…s-process, HL.
“Mixed” components… solar, Q, P3.
Cosmic ray exposure record (esp. 81Kr-Kr).
Halogen measurements after neutron.
irradiation (Cl, Br, I ⇒ Ar, Kr, Xe).
Wealth of different areas can be addressed.
2
Measuring Kr & Xe
3
Manchester Instruments
•  Resonance Ionization…
–  Tune laser(s) to transition(s) in target species.
–  Photo-Ionize from excited state.
–  Species selective.
•  Cryogenic Sample Concentrator…
–  Typically heat sample to get gas out, clean,
admit to mass spec.
–  Continuously condense onto cold spot.
–  Release once every 0.1 s and ionise in plume.
•  Time-of-flight Mass Analyser
4
Principle of Operation
2 kV
Cold Spot
1.8 kV
+
+
+
+
Pulsed
desorption
1064 nm
+
TOF MS
+
Ionizing Laser(s)
5
RELAX
•  Refrigerator Enhanced Laser Analyser for
Xenon.
•  Ideal for small amounts of gas, large
anomalies.
•  Detection limits <1000 atoms of 132Xe.
6
RIMSKI
Resonance Ionization Mass
Spectrometer for Krypton
Isotopes.
7
Resonance Ionisation of Krypton
1064 nm
558.1 nm
+
+
+
+
+
+
+
116.5 nm
+
+
+
+
8
VUV radiation production by 4-wave
difference frequency mixing
1507.3 nm
Xe/Ar
116.48nm
252.5 nm
NO
9
Spectroscopic Effects
•  Various spectroscopic effects can introduce
nonlinear mass discrimination.
•  Approach: Demonstrate stability so that
sample-standard bracketing can calibrate effect.
10
Stability: Air Samples
~50 air aliquots (106
krypton atoms each,
known composition)
analyzed over a week.
Typical
variation
within each
day.
Average
calculated
error
C6H6 interference
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Test of Stability
81Kr-Kr
Ages of Eucrites.
81Kr
(230,000 year half life) reaches equilibrium
between C.R. production and radioactive decay, use
to calibrate production rate of stable isotopes.
Typical previous sample sizes >100-300 mg.
12
Typical TOF spectra
Pasamonte 1.2 mg:
Air, 106 atoms:
Sioux County 3.3 mg:
13
81Kr-Kr
cosmic ray exposure ages of
Eucrites compared to literature values.
(Strashnov et al., in
press, GCA)
Bunburra Rockhole: 27.59±1.39 Ma
Lakangaon:
25.34±1.07 Ma
[*] Y.N. Miura et al., Geochim. Cosmochim. Acta, 1998,
62 (13), 2369-2387.
14
[*] Shukolyukov A. and Begeman F., Meteorit. Planet.
Sci., 1996, 31, 60-72.
Application to Chondrules.
(Proof of concept)
15
RIMSKI Sensitivity
5 Minutes
Fig. 2 a) 84Kr pump out curve for the air sample containing
2x105 total krypton: the Kr signal decreases as ionized
atoms are removed from the ion source and implanted into
the detector The fast signal decrease indicates efficient
ionization of atoms.
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Single Chondrule 81Kr-Kr Cosmic Ray Exposure Age determinations.
Fig.2 b) TOF spectrum collected for 10 mg
chondrule during the second heating step (11W).
The inset is enlarged 81Kr region (<1000 atoms)
(Strashnov et al., Submitted to MAPS)
17
14
Allegan chondrules 81Kr -78Kr ages
81Kr-Kr
exposure age, My
12
9 mg
10
10 mg
8
3 mg
6 mg
2 mg
Average
7 mg
2 mg
6
4
2
81Kr-Kr
ages determined
for 7 individual
chondrules separated
from Allegan H5
chondrite (filled dots).
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Summary
•  Xe & Kr analysis can provide many
insights into history of primitive material,
evolution of volatile reservoirs.
•  Most sensitive analyses currently employ
resonance ionization.
•  Detection limits <1000 atoms.
•  Sample requirements required range from
single few-micron grains up to a few
milligrams (81Kr).
19
20
Xe (atoms/1000)
5
Busemann et al. 2010
500 ± 200 atoms
132Xe
reheat
L2054 Cl1 F1
reheat
reheat
L2036 Cl20 v3p3
reheat
L2036 Cl20 v3p4
reheat
L2036 Cl9 v2p1
reheat
L2054 Cl4+L2055 Cl1
reheat
L2036 Cl9 AI2
132
10
1950 ± 140
atoms 132Xe
Blank
GSC IDPs
“normal” IDPs
0
run
400 ± 200
atoms 132Xe
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RELAX – Xenon Analyses
200 µg ALH77307 (CO3.0)
Average of 60 high temperature releases
during stepped pyrolysis experiment
(irradiated sample).
1 s.d. errors.
Can achieve about 1% error on major
isotopes for ~105 atoms.
(Crowther et al., 2009).
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Laser system
1064 nm
558 nm
1507 nm
252 nm
To the ion source
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81Kr-Kr
Allegan chondrules 81Kr -78Kr ages
12
a)
9 mg
3 mg
6 mg
10
7 mg
10 mg
8
2 mg
Average
2 mg
6
4
2
14
exposure age, My
Fig. 3
ages
determined for 7
individual chondrules
separated from Allegan
H5 chondrite (filled dots).
81Kr-Kr
81Kr-Kr
exposure age, My
14
b)
Allegan chondrules 81Kr- 80+82Kr ages
12
9 mg
10
8
Average
3 mg
10 mg
6 mg
7 mg
2 mg 2 mg
6
4
2
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Mixed Components
•  Solar Xenon (s + r + p +…)
•  Q-Xe (fractionated solar xenon + …)
•  Xe-P3
–  Released at low T from nanodiamond
separates.
–  Concentrations decrease with processing.
–  Associated with iodine.
–  Very similar to Q-Xe, except s-process deficit.
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