[P-PS24_1PM1] 宇宙における物質の形成と進化

[PPS24-06] イオン誘起微粒子核生成I：装置開発とねらい

*渡部 直樹¹、日高 宏¹、中井 陽一²、小島 隆夫³ (1.北大　低温研、2.理研　仁科センター、3.理研 原子物理研)

キーワード：微粒子, 核生成, クラスターイオン

Mechanisms of grain nucleation have attracted researchers in various fields of science in connection with e.g. atmospheric aerosols and cosmic dust grains. Although there have been many theoretical and experimental works approaching this issue, the details of nucleation mechanism is still in debate. Most of works are performed assuming homogeneous nucleation in gas phase or heterogeneous nucleation on the bulk surfaces. The homogeneous nucleation often suffers from a "critical size" of particle and requires high supersaturation condition to gain the efficient formation rate, while the nucleation on the bulk surface may not be relevant to the first stage of grain formation in realistic environments. It is know that ion-induce heterogeneous nucleation would play an important role in the particle formation because in this mechanism ion-neutral interaction overcome difficulties expected in neutral-gas-phase homogeneous nucleation. We recently developed a new experimental apparatus to investigate the elementary process of the ion-induced nucleation. We present the importance of ion-induced nucleation and advantages of the newly developed apparatus. Using this apparatus, we have been successful in obtaining an important physical parameter, free energy, of water cluster ions.