Schematic of an MHI (IMAGE) Heinrich-Heine University Duesseldorf Caption Schematic of an MHI, here an HD+ molecule: It comprises a hydrogen nucleus (p) and a deuteron nucleus (d) that can rotate around and vibrate against each other. In addition, there is an electron (e). The movements of p and d are expressed in the appearance of spectral lines. Credit HHU/Soroosh Alighanbari Usage Restrictions No restrictions. License Public Domain Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.