The detection of the free precession of co‐located 3He/129Xe nuclear spins (clock comparison) is used as ultra‐sensitive probe for non‐magnetic spin interactions, since the magnetic dipole ...interaction (Zeeman‐term) drops out in the weighted frequency difference, i.e., Δω = ωHe‐ γHe/γXe·ωXe of the respective Larmor frequencies. Recent results are reported on searches for (i) short‐range P‐ and T‐violating interactions between nucleons, and (ii) Lorentz violating signatures by monitoring the Larmor frequencies as the laboratory reference frame rotates with respect to distant stars (sidereal modulation). Finally, a new experimental initiative to search for an electric dipole moment of 129Xe (CP‐violation) is discussed, which strongly benefits from the long spin‐coherence times obtained, reaching T2,He*> 100 h and T2,Xe*> 8 h in case of 3He and 129Xe, respectively.
The detection of the free precession of co‐located 3He/129Xe nuclear spins (clock comparison) is used as ultra‐sensitive probe for non‐magnetic spin interactions, since the magnetic dipole interaction (Zeeman‐term) drops out in the weighted frequency difference, i.e., Δω = ωHe‐ γHe/γXe·ωXe of the respective Larmor frequencies. Recent results are reported on searches for (i) short‐range P‐ and T‐violating interactions between nucleons, and (ii) Lorentz violating signatures by monitoring the Larmor frequencies as the laboratory reference frame rotates with respect to distant stars (sidereal modulation). Finally, a new experimental initiative to search for an electric dipole moment of 129Xe (CP‐violation) is discussed, which strongly benefits from the long spin‐coherence times obtained, reaching T*2,He> 100 h and T*2,Xe> 8 h in case of 3He and 129Xe, respectively.
Systematic T1 improvement for hyperpolarized 129xenon Repetto, Maricel; Babcock, Earl; Blümler, Peter ...
Journal of magnetic resonance (1997),
March 2015, 2015-Mar, 2015-03-00, 20150301, Letnik:
252
Journal Article
Recenzirano
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•Very long wall relaxation times were obtained reproducibly in uncoated glass cells.•“Aging” process of wall relaxation in the same cell was identified and eliminated.•SF6 and CO2 ...were identified as efficient destroyers of Xe-dimers.•Strong dependence of van der Waals relaxation on the isotope concentration.•In summary this yields storage times for HP-129Xe of 5–7h at low magnetic fields.
The spin–lattice relaxation time T1 of hyperpolarized (HP)-129Xe was improved at typical storage conditions (i.e. low and homogeneous magnetic fields). Very long wall relaxation times T1wall of about 18h were observed in uncoated, spherical GE180 glass cells of ∅=10cm which were free of rubidium and not permanently sealed but attached to a standard glass stopcock. An “aging” process of the wall relaxation was identified by repeating measurements on the same cell. This effect could be easily removed by repeating the initial cleaning procedure. In this way, a constant wall relaxation was ensured. The Xe nuclear spin-relaxation rate 1/T1Xe–Xe due to van der Waals molecules was investigated too, by admixing three different buffer gases (N2, SF6 and CO2). Especially CO2 exhibited an unexpected high efficiency (r) in shortening the lifetime of the Xe–Xe dimers and hence prolonging the total T1 relaxation even further. These measurements also yielded an improved accuracy for the van der Waals relaxation for pure Xe (with 85% 129Xe) of T1Xe–Xe=(4.6±0.1)h. Repeating the measurements with HP 129Xe in natural abundance in mixtures with SF6, a strong dependence of T1Xe–Xe and r on the isotopic enrichment was observed, uncovering a shorter T1Xe–Xe relaxation for the 129Xe in natural composition as compared to the 85% isotopically enriched gas.
We report on precise measurements of magnetic field gradients extracted from transverse relaxation rates of precessing spin samples. The experimental approach is based on the free precession of ...gaseous, nuclear spin polarized
3
He and
129
Xe atoms in a spherical cell inside a magnetic guiding field of about 400 nT using LT
C
SQUIDs as low-noise magnetic flux detectors. The transverse relaxation rates of both spin species are simultaneously monitored as magnetic field gradients are varied. For transverse relaxation times reaching 100 h, the residual longitudinal field gradient across the spin sample could be deduced to be |
∇
B
z
| = (5.6 ± 0.2) pT/cm. The method takes advantage of the high signal-to-noise ratio with which the decaying spin precession signal can be monitored that finally leads to the exceptional accuracy to determine magnetic field gradients at the sub pT/cm scale.
Graphical abstract
We performed an experiment to search for a new spin-dependent P- and T-violating nucleon–nucleon interaction Formula: see text which is mediated by light pseudoscalar bosons such as axions or ...axionlike particles. This interaction causes a shift Formula: see text in the precession frequency of nuclear spin polarized gases in the presence of an unpolarized mass. In order to measure this frequency shift a
3
He/Formula: see textXe comagnetometer was used which is based on the detection of free precession of
3
He and Formula: see textXe nuclear spins using SQUIDs as detectors. For the upper limit of Formula: see text we obtained 7.1Formula: see textnHz. With this value, an upper limit of the scalar-pseudoscalar coupling of the axion to the spin of a bound neutron could be deduced within the axion mass window. For axion masses between 2 and 500Formula: see textFormula: see texteV, the laboratory upper bounds were improved by up to 4 orders of magnitude.
We performed an experiment to search for a new spin-dependent P- and T-violating nucleon–nucleon interaction
σ
→
⋅
r
̂
which is mediated by light pseudoscalar bosons such as axions or axionlike ...particles. This interaction causes a shift
Δ
ν
in the precession frequency of nuclear spin polarized gases in the presence of an unpolarized mass. In order to measure this frequency shift a 3He/
1
2
9
Xe comagnetometer was used which is based on the detection of free precession of 3He and
1
2
9
Xe nuclear spins using SQUIDs as detectors. For the upper limit of
Δ
ν
sp
we obtained 7.1
nHz. With this value, an upper limit of the scalar-pseudoscalar coupling of the axion to the spin of a bound neutron could be deduced within the axion mass window. For axion masses between 2 and 500
μ
eV, the laboratory upper bounds were improved by up to 4 orders of magnitude.
We report on the search for a new spin-dependent P- and T-violating interaction between nucleons mediated by light, pseudoscalar bosons such as the axion which was invented to solve the strong CP ...problem. Our experimental approach is to use an ultra-sensitive low-field magnetometer based on the detection of free precession of co-located 3He and 129Xe nuclear spins using SQUIDs as low-noise magnetic flux detectors. In the presence of an unpolarized mass the precession frequency shif
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