科研之友
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摘要
Mass spectrometry, coupled with position-sensitive coincidence detection, has been used to investigate the reactions of N-2(2+) with various small hydrocarbon molecules (C2H4, C2H6, C3H4, c-C3H6 and n-C3H6) at collision energies below 10 eV in the centre-of-mass frame. The reactivity, in each case, is dominated by electron transfer. However, in each collision system we also clearly identify products formed following the creation of new chemical bonds. These bond-forming reactions comprise two distinct classes: (i) hydride transfer reactions which initially form NnH+ (n = 1, 2) and (ii) N+ transfer reactions which form monocationic products with C-N bonds. These bond-forming reactions make a small (5-10%), but significant, contribution to the overall product ion yield in each collision system. The temporal and positional data recorded by our coincidence detection technique are used to construct scattering diagrams which reveal the mechanisms of the bond-forming reactions. For the hydride transfer process, the scattering diagrams reveal that H- is directly transferred from the hydrocarbon to N-2(2+) at significant interspecies separations. For the hydride transfer reactions with C2H4, C2H6 and C3H4, we observe fragmentation of the nascent N2H+* to form NH+ + N. The N+ transfer reaction also proceeds by a direct mechanism: a single step involving N+/H exchange results in the formation of a singly-charged organic species containing a C-N bond which is detected in coincidence with H+. The two general classes of bond-forming reactivity we observe in the reactions of N-2(2+) with organic molecules may be relevant in the chemistry of energised environments rich in molecular nitrogen and hydrocarbon species, such as the atmosphere of Titan.
- 出版日期2015-2-1
