We observed two-photon emission signal from the first vibrationally excited state of parahydrogen gas coherently excited by counter-propagating laser pulses. A single narrow-linewidth laser source has roles in the excitation of the parahydrogen molecules and the induction of the two-photon emission process. We measured dependences of the signal energy on the detuning, target gas pressure, and input pulse energies. These results are qualitatively consistent with those obtained by numerical simulations based on Maxwell-Bloch equations with one spatial dimension and one temporal dimension. This study of the two-photon emission process in the counter-propagating injection scheme is an important step toward neutrino mass spectroscopy.

Traditional “magic numbers” were once regarded as immutable throughout the nuclear chart. However, unexpected changes were found for unstable nuclei around N = 20. With both proton and neutron numbers around the magic number of 20, the neutron-rich 39Cl isotope provides a good test case for the study of the quantum-state evolution across the major shell. In the present work, the negative parity states in 39Cl are investigated through the β decay spectroscopy of 39S. Newly observed γ transitions together with a new state are assigned into the level scheme of 39Cl. The spin parity of 5/2− for the lowest negative parity state in 39Cl is reconfirmed using the combined γ transition information. These systematic observations of the negative parity states in 39Cl allow a comprehensive comparison with the theoretical descriptions. The lowest 5/2− state in 39Cl remains exotic in terms of comparisons with existing theoretical calculations and with the neighboring isotopes having similar single-particle configurations. Further experimental and theoretical investigations are suggested.

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The gyromagnetic factor of the low-lying E = 251.96(9) keV isomeric state of the nucleus 99 Zr was measured using the Time Dependent Perturbed Angular Distribution technique. This level is assigned a spin and parity of J π = 7/2 + , with a half-life of T 1/2 = 336(5) ns. The isomer was produced and spin-aligned via the abrasion-fission of a 238 U primary beam at RIBF. A magnetic moment |µ| = 2.31( 14)µN was deduced showing that this isomer is not single-particle in nature. A comparison of the experimental values with Interacting Boson-Fermion Model IBFM-1 results shows that this state is strongly mixed with a main νd 5/2 composition. Furthermore it was found that monopole single-particle evolution changes significantly with the appearance of collective modes, likely due to type-II shell evolution.