Recoil-ion momentum analyses of single-electron capture of He by B(4+,5+) at 0.5 - 1 MeV/nucleon

Abstract

State-selective measurements of differential cross sections of one-electron capture processes from helium atoms by fast boron ions were made. All the momentum components of the recoil He(+) ion were measured with Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS) in coincidence with the projectile which captured one electron. Recoil ions were analyzed by an electrostatic spectrometer in coincidence with the projectile ions detected by a deflecting magnet system. The differential cross sections for these final states were obtained as functions of the transverse component. The electron capture predominantly occurred into the excited states, but the relative intensity of the capture into the ground state increased rapidly with the collision energy. The experimental results of the differential cross sections were compared with calculations of the eikonal approximation. The theoretical predictions for the capture to the excited states agreed well with the experimental results at all the projectile velocities and charge states. The theory could well reproduce the hump structure in the differential cross section for the capture to the ground state.

高速硼素イオンによるHe原子の1電子捕獲過程の微分断面積の状態選択型測定を行った。1電子を捕獲する入射体と同期して冷ターゲット反跳イオン運動量分光法(COLTRIMS)を用いて、反跳He(+)イオンの全運動量成分を測定した。反跳イオンは静電型分光計で解析し、電磁石解析系で測定した入射イオンと同時に測定した。終状態の微分断面積を運動量の横成分の関数として求めた。電子捕獲は主として励起状態へ生じたが、基底状態への捕獲の相対強度は衝突エネルギーとともに急増した。微分断面積の曲線に現れたこぶの形は衝突速度と入射体の電荷に依存していた。微分断面積の実験結果をアイコナール近似の計算と比較した。励起状態への捕獲の理論的予測はすべての入射体速度と荷電状態で実験結果と良く一致した。基底状態への捕獲の微分断面積におけるこぶ構造をこの理論は良く再現できた。