Development of the collection apparatus for recoil products for study of the deexcitation process of 235mU

235^m U has very low excitation energy (76.8 eV) and decays predominantly by the internal conversion process. Because the deexcitation of 235^mU is caused by the interaction between the nucleus and outer-shell electrons, the variation of the decay constant depending on its chemical environment was reported. We are aiming to clarify the deexcitation process of 235^mU by measuring the decay constants and the energy spectra of the internal-conversion electrons for 235^mU with various chemical forms. In this work, we developed an apparatus for collecting 235^mU recoiling out of ²³⁹Pu. We evaluated the performance of the apparatus by using ²²⁴Ra recoiling out of ²²⁸Th. The collection yields of ²²⁴Ra were determined in various applied voltages, air pressures, and ²²⁸Th source shapes. Based on these results, we determined suitable experimental conditions for the collection of 235^mU from ²³⁹Pu. In addition, the detection apparatus for the low-energy internal-conversion electrons are under development.