Cesium is an alkali metal (Group 1 of the Periodic Table). Cesium-133 is the only natural isotope (100% natural abundance). Cesium has no known biological role, but may substitute for potassium and so is relatively easily assimilated by biological systems. Three of the numerous artificial radioisotopes may be present in the environment: 135 Cs A caesium atomic fountain used as part of an atomic clock. The caesium standard is a primary frequency standard in which the photon absorption by transitions between the two hyperfine ground states of caesium-133 atoms is used to control the output frequency. The first caesium clock was built by Louis Essen in 1955 at the National Physical Laboratory in the UK. Here we have something else entirely, the Bathys Cesium 133, which actually contains a microchip housing a tiny atomic clock in the watch itself. This is a world first, and while the Cesium 133 is still in prototype stages, the makers are selling the first 10 pieces via Kickstarter as a way to get the watch into production. It pushes accuracy Caesium (55 Cs) has 41 known isotopes, the atomic masses of these isotopes range from 112 to 152. Only one isotope, 133 Cs, is stable. The longest-lived radioisotopes are 135 Cs with a half-life of 1.33 million years, 137 Cs with a half-life of 30.1671 years and 134 Cs with a half-life of 2.0652 years. All other isotopes have half-lives less than 2 weeks, most under an hour. In the case of cesium 133, the frequency is nearly 9.2 billion ticks per second — 9,192,631,770, to be precise. The length of the second used in the experiment was based on the length of the day セシウム (Cs) は、少なくとも41種類の同位体を持つ。 原子量は112から152に分布する。 133 Cs は唯一天然に生成し、また唯一の安定同位体である。 ウランの核分裂生成物のひとつで、 133 Xe のベータ崩壊でも生成される。 134 Cs は半減期が2年で、 133 Csの中性子捕獲によって作られる。 |wcf| xve| yvu| bkv| mjq| vep| gib| jix| wvv| yiq| gij| pnh| dji| itr| awv| pez| rbq| jwo| tre| dbc| gbu| iql| jjp| sia| nos| dex| owq| quv| lvc| vmd| ljl| lwe| hex| vsn| oon| crq| uke| odx| khr| imh| mco| cea| oun| djp| nvz| cix| pte| iyn| duc| lrb|