Selective Field-Ionization Electron Detector at Low Temperature of 10 mK Range (NUCLEAR SCIENCE RESEARCH FACILITY?Particle and Photon Beams)

Combined with a dilution refrigerator, selective field-ionization detection system with a channel electron multiplier optimized at 10 mK-range temperature was developed. The detection efficiency of the ionized electrons from the n~110 Rydberg states of Rb is 98% at the lowest achieved temperature of 12 mK

Different mechanism of two-proton emission from proton-rich nuclei 23^{23}Al and 22^{22}Mg

Two-proton relative momentum ($q_{pp}$) and opening angle ($\theta_{pp}$) distributions from the three-body decay of two excited proton-rich nuclei, namely $^{23}$Al $\rightarrow$ p + p + $^{21}$Na and $^{22}$Mg $\rightarrow$ p + p + $^{20}$Ne, have been measured with the projectile fragment separator (RIPS) at the RIKEN RI Beam Factory. An evident peak at $q_{pp}\sim20$ MeV/c as well as a peak in $\theta_{pp}$ around 30$^\circ$ are seen in the two-proton break-up channel from a highly-excited $^{22}$Mg. In contrast, such peaks are absent for the $^{23}$Al case. It is concluded that the two-proton emission mechanism of excited $^{22}$Mg is quite different from the $^{23}$Al case, with the former having a favorable diproton emission component at a highly excited state and the latter dominated by the sequential decay process

A new species of notodelphyid copepod associated with Ρterygascidia longa (Van Name, 1918) from the Basilan Strait, Philippines

In research on the two ascidians Pterygascidia mirabilis Sluiter, 1904, and P. longa (Van Name, 1918), Tokioka (1971a, b) found some copepods associated with both species. We were given the opportunity to examine these crustaceans. The copepod described below, Goniodelphys tokiokai n. sp., is a notodelphyid inhabiting the branchial sac of P. longa. The material was obtained from a few specimens among 20 ascidians which were collected by the Snellius Expedition on 5 September 1929, and deposited at the Rijksmuseum van Natuurlijke Historie, Leiden. As the copepods living in P. mirabilis belong to a family other than Notodelphyidae they will be reported in a future paper. We wish to express our warm thanks to Dr. Takasi Tokioka, of the Seto Marine Biological Laboratory, for collecting the copepods from the ascidians and providing us the opportunity to examine the specimens, and for many other favors. We are indebted to the Rijksmuseum van Natuurlijke Historie, Leiden, for permission to study the material. Goniodelphys tokiokai n. sp. Specimens examined: 6 females, all adult, from Pterygascidia longa (Van Name, 1918) preserved in formalin, Snellius Expedition, Station 60, 6° 58'N 1210 52.5Έ, in the Basilan Strait between the islands of Basilan and Mindanao, 72-80 m deep, September 5, 1929. Types. — The types are preserved in the collection of the Rijksmuseum van Natuurlijke Historie, Leiden. The holotype under no. Crust. F 793, a paratype under no. Crust. F 794. Description. — Female (figs. 1-4). Body (fig. 1a) compressed, rigid from heavy cuticularization of integument. Three major body divisions, cephalo

Coherent Time Evolution of Highly Excited Rydberg States in Pulsed Electric Field: Opening a New Scheme for Stringently Selective Field Ionization (NUCLEAR SCIENCE RESEARCH FACILITY-Beams and Fundamental Reaction)

Coherent time evolution of highly excited Rydberg states in Rb (98 n 150) under pulsed electric field in high slew rate regime was investigated with the field ionization detection. We observed for the first time a discrete transition of the threshold ionization field with slew rate, the behavior of which depends also on the position of the low l states relative to the adjacent manifold. The experimental results strongly suggest that the coherent interference effect plays decisive role for such transitional behavior, and bring us a new, quite effective scheme for the stringently selective field ionization