射频离子阱中N^(2+)与N_2碰撞电荷转移研究

Study of Charge Transfer Collision of N^(2+) with N_2 in an RF Ion Trap

用电子轰击的方法在射频离子阱中产生和囚禁N2+，并通过质量选择囚禁和抛出检测研究了平衡能量约为1．4eV的N1+与N2的低能热碰撞过程，测量得到了电荷转移速率系数为1．89（0．56）×10－9cm3s-1。与理论计算值Langevin速率系数和他人在不同条件下的实验值符合．

The charge-transfer rate coefficients for reaction M2+ (2s2p, 2P0)+N2→ products is measured by recording the the dependence of the M2+ stored in an ion trap. A quadrupole radio-frequency ion trap was used to trap N2+ produced by electron bombardment,With operating the trap near the cross point of βz=1 and βr=0 of the first stability region (i.e. the operating point of az=0.15, qz=0.78), N2+ with equilibrium energy of about 1.4 eV have been seledively confined in the trap.After the mass selective storage and charge transfer collision processes the produced ions have been ejectal from the trap and detected. The dacay of the N2+ signals was analyzed by single exponential least-squares fits to the data, the obtained decay rates represented corresponding charge-transfer rates. We repeatal these measurements under five different reactant gas N2 pressures and obtained the variation of the charge-transfer rates versus the N2 pressures.The charge-transfer rate coefficient have ho evaluated to be 1.89 (0.56)×10-9cm3s-1.The uncertainty presental here is due to the uncertainty of the gas pressure measurernents and the uncertainty of the ion signal intensity resulted from the fluctuation of laser power and other nonlinear effects of the detection circuit.Our measured result is in good agreement with theoretical Langevin rate coefficient of 2.6×10-9cm3s-1. It is also in agreement with Kwong's experimental value of 2.1 (0.18)×10-9cm3s-1 measured in a cylindrical RF ion trap at equilibrium energy of 2.7eV, and is consistent with Church's early published value of 2.8 (0.6)×10-9cm3-1 obtained in a Penning trap with equilibrium energy larger than 3eV.