Tiefenthaler Lukas, Kollotzek Siegfried, Ellis Andrew M, Scheier Paul, Echt Olof
Institut für Ionenphysik und Angewandte Physik Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria.
Phys Chem Chem Phys. 2020 Dec 23;22(48):28165-28172. doi: 10.1039/d0cp05174h.
We demonstrate a novel method to ionize molecules or molecular clusters by proton transfer at temperatures below 1 K. The method yields nascent ions and largely eliminates secondary reactions, even for notoriously 'delicate' molecules. Protonation is achieved inside liquid helium nanodroplets (HNDs) and begins with the formation of (H2)mH+ ions as the proton donors. In a separate and subsequent step the HNDs are doped with a proton acceptor molecule, X. Proton transfer occurs between X and the cold proton donor ions inside a helium droplet, an approach that avoids the large excess energy that is released if HNDs are first doped and then ionized. Mass spectra, recorded after stripping excess helium and hydrogen in a collision cell, show that this method offers a new way to determine proton affinities of molecules and clusters by proton-transfer bracketing, to investigate astrochemically relevant ion-molecule reactions at sub-kelvin temperatures, and to prepare XH+ ions that are suitable for messenger-tagging action spectroscopy.
我们展示了一种在低于1K的温度下通过质子转移使分子或分子簇离子化的新方法。该方法能产生新生离子，并在很大程度上消除二级反应，即使对于极其“脆弱”的分子也是如此。质子化在液氦纳米滴（HNDs）内部实现，始于作为质子供体的(H2)mH+离子的形成。在单独的后续步骤中，HNDs被掺杂一种质子受体分子X。质子转移发生在X与氦滴内部的冷质子供体离子之间，这种方法避免了如果先对HNDs进行掺杂然后再离子化时释放的大量多余能量。在碰撞池中去除多余的氦和氢后记录的质谱表明，该方法提供了一种通过质子转移括弧法确定分子和簇的质子亲和力、研究亚开尔文温度下与天体化学相关的离子 - 分子反应以及制备适用于信使标记作用光谱的XH+离子的新途径。
