The emission of electron pairs from surfaces has the power to reveal details about the electron–electron interaction in condensed matter. This process, stimulated by a primary electron or photon beam, has been studied both in experiment and theory over the last two decades. An additional pathway, namely positron–electron pair emission, holds the promise to provide additional information. It is based on the notion that the Pauli exclusion principle does not need to be considered for this process.

We have commissioned a laboratory based positron source and performed a systematic study on a variety of solid surfaces. In a symmetric emission geometry we can explore the fact that positron and electron are distinguishable particles. Following fundamental symmetry arguments we have to expect that the available energy is shared unequally among positron and electron. Experimentally we observe such a behavior for all materials studied. We find an universal feature for all materials in the sense that on average the positron carries a larger fraction of the available energy. This is qualitatively accounted for by a simplified scattering model. Numerical results, which we obtained by a microscopic theory of positron–electron emission from surfaces, reveal however that there are also cases in which the electron carries more energy. Whether the positron or the electron is more energetic depends on details of the bound electron state and of the emission geometry. The coincidence intensity is strongly material dependent and there exists an almost monotonic relation between the singles and coincidence intensity. These results resemble the findings obtained in electron and photon stimulated electron pair emission. An additional reaction channel is the emission of an electron pair upon positron impact. We will discuss the energy distributions and the material dependence of the coincidence signal which shows similar features as those for positron–electron pairs.

从表面发射电子对有能力揭示凝聚态物质中电子-电子相互作用的细节。在过去的二十年里，这个过程由初级电子或光子束激发，在实验和理论中都得到了研究。另一种途径，即正电子-电子对发射，有望提供额外的信息。它基于这样一个概念，即此过程不需要考虑泡利不相容原理。

我们委托了一个基于实验室的正电子源，并对各种固体表面进行了系统研究。在对称发射几何中，我们可以探索正电子和电子是可区分的粒子这一事实。遵循基本的对称性论证，我们必须期望可用能量在正电子和电子之间不平等地共享。通过实验，我们观察到所有研究的材料的这种行为。我们发现所有材料的普遍特征是正电子平均携带大部分可用能量。这由简化的散射模型定性地解释。我们通过表面正电子-电子发射的微观理论获得的数值结果表明，也存在电子携带更多能量的情况。正电子还是电子的能量更高取决于束缚电子状态和发射几何的细节。重合强度强烈依赖于材料，并且在单曲和重合强度之间存在几乎单调的关系。这些结果类似于在电子和光子受激电子对发射中获得的发现。另一个反应通道是在正电子撞击时发射电子对。我们将讨论符合信号的能量分布和材料依赖性，该信号显示出与正电子-电子对相似的特征。重合强度强烈依赖于材料，并且在单曲和重合强度之间存在几乎单调的关系。这些结果类似于在电子和光子受激电子对发射中获得的发现。另一个反应通道是在正电子撞击时发射电子对。我们将讨论符合信号的能量分布和材料依赖性，该信号显示出与正电子-电子对相似的特征。重合强度强烈依赖于材料，并且在单曲和重合强度之间存在几乎单调的关系。这些结果类似于在电子和光子受激电子对发射中获得的发现。另一个反应通道是在正电子撞击时发射电子对。我们将讨论符合信号的能量分布和材料依赖性，该信号显示出与正电子-电子对相似的特征。