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A search for double β decay of dysprosium was realized for the first time with the help of an ultra-low background HP Ge γ detector. After 2512 h of data taking with a 322 g sample of dysprosium oxide limits on double beta processes in 156Dy and 158Dy have been established on the level of T1/2?10141016 yrT1/2?10141016 yr. Possible resonant double electron captures in 156Dy and 158Dy were restricted on a similar level. As a by-product of the experiment we have measured the radioactive contamination of the Dy2O3 sample and set limits on the α   decay of dysprosium isotopes to the excited levels of daughter nuclei as T1/2?10151017 yrT1/2?10151017 yr.  相似文献   

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The results of an experiment on transmitting UCN through a rotating disc made of silicon single crystal are reported. They demonstrate that the transmission of the sample remains constant if it moves parallel to its surface. The range of neutron velocities in the system of reference associated with the sample is 6–38 m/s638 m/s. It is found that the real and imaginary parts of the effective potential are constant to within 3×10−33×103.  相似文献   

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This work reports on the phonon energy inversion in graphene nanoribbons: after initial localized thermal excitation, the energy of initial cold phonons (flexural mode: FM) becomes higher than that of local hot phonons (longitudinal and transverse modes: LM/TM). Such energy inversion holds for about 50 picoseconds. Two physical factors combine together to give rise of this phenomenon: one is the much faster heat conduction by FM phonons than that by LM/TM phonons, and the other factor is the strongly temperature-dependent energy exchange rate between FM and LM/TM phonons: 3.7×1010 s−13.7×1010 s1 at 84 K to 20.3×1010 s−120.3×1010 s1 at around 510 K.  相似文献   

5.
Three-mode opto-acoustic interactions can excite acoustic modes of the mirrors of an optical cavity. This was achieved when the frequency difference between the fundamental and higher order optical mode matches the frequency of appropriate acoustic mode of the mirror. The excitation also critically depends on the spatial overlap between acoustic and optical modes. In this Letter, we use a controlled CO2 laser to thermally change the radius of curvature of one mirror of an 80 m Fabry–Pérot cavity for three-mode interaction. Several acoustic modes of the cavity end mirror were observed with quality factors of ∼105–106105106 at the thermal noise level.  相似文献   

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A neutral Dirac fermion ψ   with a nonzero magnetic dipole moment is supplied as a singlet within the context of the standard model and is considered as a dark matter candidate near the electroweak scale (10–1000 GeV101000 GeV). We discuss its dynamics with the ordinary matters through the magnetic dipole moment. The magnetic dipole moment constrained by the relic abundance may be as large as 10−1810−17e⋅cm10181017ecm. We show that the elastic scattering is due to a spin–spin interaction for the direct detections and the predictions are under experimental exclusion limits of the current direct detectors, XENON10 and CDMS II, and consider the possibility of dark matter detection in the future.  相似文献   

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Accurate calculations for the ground state of the molecular ions He3+2 and HeH2+ placed in a strong magnetic field B?102 a.u.B?102 a.u. (≈2.35×1011 G2.35×1011 G) using the Lagrange-mesh method are presented. The Born–Oppenheimer approximation of zero order (infinitely massive centers) and the parallel configuration (molecular axis parallel to the magnetic field) are considered. Total energies are found with 9–10 s.d. The obtained results show that the molecular ions He3+2 and HeH2+ exist at B>100 a.u.B>100 a.u. and B>1000 a.u.B>1000 a.u., respectively, as predicted in Turbiner and López Vieyra (2007) [1] while a saddle point in the potential curve appears for the first time at B∼80 a.u.B80 a.u. and B∼740 a.u.B740 a.u., respectively.  相似文献   

8.
Ignition of nuclear fusion flames in solid state density fuel following Chu?s model of 1972 is evaluated using now available plasma blocks from ultrahigh acceleration with laser pulses of picosecond (ps) duration and power up to and beyond petawatt (PW). A new numerical approach is reported where genuine two-fluid hydrodynamics is used in order to study the shock mechanism of the generated fusion flame, its propagation velocities above 1000 km/s1000 km/s, and fusion efficiencies for deuterium–tritium needing an energy flux of 108 J/cm2108 J/cm2. The results of the built-up of the shock process are reported showing a basic difference between the ps and nanosecond (ns) properties.  相似文献   

9.
A search for solar axions has been performed using an axion helioscope which is equipped with a 2.3-m long 4 T superconducting magnet, a gas container to hold dispersion-matching gas, PIN-photodiode X-ray detectors, and a telescope mount mechanism to track the sun. A mass region around ma=1 eVma=1 eV was newly explored. From the absence of any evidence, analysis sets a limit on axion–photon coupling constant to be gaγγ<5.6–13.4×10−10 GeV−1gaγγ<5.613.4×10−10 GeV−1 for the axion mass of 0.84<ma<1.00 eV0.84<ma<1.00 eV at 95% confidence level. It is the first result to search for the axion in the gaγγ–magaγγma parameter region of the preferred axion models with a magnetic helioscope.  相似文献   

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