HeH+ is a very simple molecule, consisting only of an alpha-particle (the He nucleus), a proton (the H nucleus), and two electrons. In addition, it is thought to be the very first diatomic molecule formed when the early universe cooled down, and it has even been detected in our galaxy.
Therefore, we investigated the fundamental rotational transition of HHe+, which is at a high frequency of 2.010 THz. This is quite a challenge, as such an investigation requires a high-resolution source at 2 THz, and is best done in a low temperature ion trapping machine. Using different spectroscopic techniques, we determined the transition frequency value to 2010.183312(8) GHz, which is 10 times more accurate than a former measurement. This successful investigation was made possible by a collaboration of many scientists from SFB1601, including astronomers, instrumentation specialists and laboratory spectroscopists.
