Figure 2: Time-of-flight spectrum over a distance of 49 cm, of hydrogen metastable atoms ( , ) going out of a Stern-Gerlach atom interferometer (see text). The atom velocity is 10 km s−1. Open circles: a comoving field is used as a phase object. The value is chosen to get a central bright fringe. The spatial period is and a unique frequency is used. The field velocity is  s−1, which corresponds to the time of flight indicated by a vertical (red) arrow. Light line: time-of-flight spectrum without the interferometer.