ミュオン・ミュオニウム化学研究のすすめ

Abstract

正または負電荷を有するミュオンを利用すると，ミュオニウム(0.114 amu) およびミュオニックヘリウム(4.11 amu)と呼ばれる軽い水素同位体および重い水素同位体をつくりだすことができる．こうした水素同位体を利用することによって新しい化学研究を展開できる可能性がある．本稿では，これまで行われてきた量子論に基づいたミュオニウム関連分子の理論研究を紹介し，その特異性について解説する．

Figures

Figure 1.

 Schematic potential energy diagrams of (a) HeXHe⁺ and (b) NeXNe⁺ (X = Mu, H) and their vibrational energy levels.

Figure 2.

 Three-dimensional perspective plot of nuclear density distribution of HeMuHe⁺ in the vibrational ground state.

Figure 3.

 (a) Three-dimensional perspective plots of quantum nuclear density distributions in the Mu-substituted glycine–K⁺ complex obtained from path-integral molecular dynamics simulations at T = 300 K. (b) Two-dimensional potential energy surface for the proton transfer process as a function of OMu and ON distances along with Mu the distribution.

Figure 4.

 (a) Molecular structure of porphycene. (b) Nuclear distributions for the Mu-substituted porphycene obtained from path-integral molecular dynamics simulations.

Figure 5.

 (a) Vibrationally adiabatic energy profiles along the intrinsic reaction coordinate for the H/Mu + pyrazine addition reactions. (b) Arrhenius plot of rate constants for the H/Mu + pyrazine reactions calculated with the transition-state theory including multi-dimensional tunneling contribution.

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