Zeller Stefan, Kunitski Maksim, Voigtsberger Jörg, Kalinin Anton, Schottelius Alexander, Schober Carl, Waitz Markus, Sann Hendrik, Hartung Alexander, Bauer Tobias, Pitzer Martin, Trinter Florian, Goihl Christoph, Janke Christian, Richter Martin, Kastirke Gregor, Weller Miriam, Czasch Achim, Kitzler Markus, Braune Markus, Grisenti Robert E, Schöllkopf Wieland, Schmidt Lothar Ph H, Schöffler Markus S, Williams Joshua B, Jahnke Till, Dörner Reinhard
Institut für Kernphysik, Goethe-Universität Frankfurt, 60438 Frankfurt, Germany;
Institut für Kernphysik, Goethe-Universität Frankfurt, 60438 Frankfurt, Germany.
Proc Natl Acad Sci U S A. 2016 Dec 20;113(51):14651-14655. doi: 10.1073/pnas.1610688113. Epub 2016 Dec 6.
Quantum tunneling is a ubiquitous phenomenon in nature and crucial for many technological applications. It allows quantum particles to reach regions in space which are energetically not accessible according to classical mechanics. In this "tunneling region," the particle density is known to decay exponentially. This behavior is universal across all energy scales from nuclear physics to chemistry and solid state systems. Although typically only a small fraction of a particle wavefunction extends into the tunneling region, we present here an extreme quantum system: a gigantic molecule consisting of two helium atoms, with an 80% probability that its two nuclei will be found in this classical forbidden region. This circumstance allows us to directly image the exponentially decaying density of a tunneling particle, which we achieved for over two orders of magnitude. Imaging a tunneling particle shows one of the few features of our world that is truly universal: the probability to find one of the constituents of bound matter far away is never zero but decreases exponentially. The results were obtained by Coulomb explosion imaging using a free electron laser and furthermore yielded He's binding energy of [Formula: see text] neV, which is in agreement with most recent calculations.
量子隧穿是自然界中普遍存在的现象，对许多技术应用至关重要。它使量子粒子能够到达根据经典力学在能量上无法到达的空间区域。在这个“隧穿区域”，粒子密度呈指数衰减。这种行为在从核物理到化学和固态系统的所有能量尺度上都是普遍存在的。尽管通常只有一小部分粒子波函数延伸到隧穿区域，但我们在此展示了一个极端量子系统：一个由两个氦原子组成的巨型分子，其两个原子核有80%的概率会出现在这个经典禁区。这种情况使我们能够直接成像隧穿粒子的指数衰减密度，我们实现了超过两个数量级的成像。对隧穿粒子进行成像展示了我们这个世界真正普遍存在的少数特征之一：在远处找到束缚态物质的一个组成部分的概率永远不为零，但会呈指数下降。这些结果是通过使用自由电子激光的库仑爆炸成像获得的，此外还得出氦的结合能为[公式：见原文]纳电子伏特，这与最近的计算结果一致。
