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The low-lying isomeric state of $^{229}$Th provides unique opportunities for high-resolution laser spectroscopy of the atomic nucleus. We determine the energy of this isomeric state by taking the absolute energy difference between the excitation energy required to populate the 29.2-keV state from the ground-state and the energy emitted in its decay to the isomeric excited state. A transition-edge sensor microcalorimeter was used to measure the absolute energy of the 29.2-keV $\gamma$-ray. Together with the cross-band transition energy (29.2 keV$\to$ground) and the branching ratio of the 29.2-keV state measured in a recent study, the isomer energy was determined to be 8.30$\pm$0.92 eV. Our result is in agreement with latest measurements based on different experimental techniques, which further confirms that the isomeric state of $^{229}$Th is in the laser-accessible vacuum ultraviolet range., Comment: 6 pages, 4 figures, 2 tables

$\alpha$ decaying states of $^{44, 46, 52}$Ti were investigated with angular correlation functions between $t$ and $\alpha$ with the $^{40, 42, 48}$Ca($^7$Li, $t\alpha$)$^{40, 42, 48}$Ca reactions at E = 26.0 MeV. Many $\alpha$ cluster states were newly observed in the 10 - 15 MeV excitation energy of $^{44}$Ti and their spin-parities were assigned, in which $J^\pi=7^-$ state was found at 11.95 MeV as a candidate for the member of the $K=0_1^-$ negative parity band. In $^{46}$Ti many $\alpha$ cluster states were also found in the 11 - 17 MeV excitation energy with the $^{42}$Ca($^7$Li, $t\alpha$)$^{42}$Ca reaction, though its strength is weak compared to $^{44}$Ti. No $\alpha$ cluster states were detected for the $^{48}$Ca($^7$Li, $t\alpha$)$^{48}$Ca reaction, in which the number of coincidence events decaying from $^{48}$Ca was very small.

Electronic structures of the filled-skutterudite compounds PrRu$_4$P$_{12}$ and SmRu$_4$P$_{12}$, which undergo a metal-insulator transition (MIT) at $T_{\rm MI}$ = 60 K and 16 K, respectively, have been studied by means of optical spectroscopy. Their optical conductivity spectra develop an energy gap of $\sim$ 10 meV below $T_{\rm MI}$. The observed characteristics of the energy gap are qualitatively different from those of the Kondo semiconductors. In addition, optical phonon peaks in the spectra show anomalies upon the MIT, including broadening and shifts at $T_{\rm MI}$ and an appearance of new peaks below $T_{\rm MI}$. These results are discussed in terms of density waves or orbital ordering previously predicted for these compounds., Comment: 4pages, 4figures, submitted to Physical Review B