Positron annihilation in the near surface of room temperature ionic liquids

Hirade, Tetsuya  ; O'Rourke, B. E.*; Kobayashi, Yoshinori*

We tried to observe the positron annihilation rates near surface of (room temperature ionic liquids) IL's, such as N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide (TMPA-TFSI) by use of the perpendicular slow positron beamline installed at AIST. The vaper pressure of TMPA-TFSI is very small and hence it is possible to measure the positron annihilation rate in vacuum chamber directly. This represents the first energy variable experimental results of the positron annihilation rate at the near surface of an IL. The triplet positronium annihilation rate seems to be larger at nearer region to the surface of the IL's.