Electron spin resonance investigation of H_2 ~+, HD ~+, and D_2 ~+ isolated in neon matrices at 2 K

摘要

Various isotopologues of natures simplest molecule, namely H _2 ~+, HD~+, and D2 +, have been isolated in neon matrices at 2 K for the first time and studied by electron spin resonance (ESR). Over many years, hundreds of matrix isolation experiments employing a variety of deposition conditions and ion generation methods have been tried to trap the H_2 ~+ cation radical in our laboratory. The molecule has been well characterized in the gas phase and by theoretical methods. The observed magnetic parameters for H_2 ~+ in neon at 2 K are: g ≈ g 2.0022(1); A_(iso)(H) 881(7) MHz; and A_(dip)(H) 33(3) MHz. Reasonable agreement with gas phase values of the isotropic hyperfine interaction (A_(iso)) is observed; however, the neon matrix dipolar hyperfine interaction (A_(dip)) is noticeably below the gas phase value. The smaller matrix value of A dip is attributable to motional averaging of the H_2 ~+ radical in the neon matrix trapping site-an occurrence that would prevent the full extent of the hyperfine anisotropy from being measured for a powder pattern type ESR sample.