The Formation of Stable H4+ by Reaction

A Penning ion trap was used to generate H4+ by reaction H2+ +H2 at very low pres-sures.The original H2+ were produced by electron impact.Subseqently reaction occurred.The dominant reaction product was H3+ but a significant H4+ signal was observed at suitable H2 pressure and delay time interval.Statistical mean energy of the H2+ was about 0.65eV.It is found that the reaction H2+ +H2→H3++H probability is largeat low energy (≤1eV).Asa reslut,the mojority of the H2+ transformed to H3+.Only very small proportion of reaction products was stable intermediate H4+.Because the depth of H4+ potential energy surface minimum is very shallow,only the H2+ with very slow velocity can probably react with H2 to produce stable H4+.The proportion of H3+ to H4+ was about 4:1 from our experimental data.It is estimated by statistical distribution law that the H2+ with low energy less than 0.4eV can proba～-bly form stable H4+ species.Because H4+ signal occurred after long delay time (i.e.trappinginterval),it is positively concluded that the H4+ were formed by reaction H2++H2→H4+.The trapping interval is of the order of 0.1s.Any quasibound H4+ would have decayed at times short relative to 0.1s and hence the H4+ signal corresponds to stable H4+.It is much longer than order of 10-6s measured before by Kirchner.