Experiments involving trapping, absorption, and transport of photons from one line by another require very accurate knowledge of line positions. On the right, line concept is shown where the 3d9 4p3/2 4P1/2 (J=1) level in Ni-like W (element 74) is excited by photopumping with an X-ray transition that is resonant. Theoretical calculation predict several candidate lines to accomplish such resonant photopumping as shown in Fig 2. These are transitions in H-like Al12+, Ni-like Er40+, and Ne-like Br25+. These schemes work only if the lines are truly resonant. Because the ions involved are very complex, theoretical calculations are only accurate to within about 1 part in 1000. Measurement with at least 10 times higher accuracy are needed to verify whether or not the levels are truly in resonance.
Results of our EBIT measurement are shown to the right. These measurements achieved an accuracy of 1 part in 20000 (20 times higher than the theoretical modeling). Unfortunately none of the predicted resonances exist. The EBIT measurements can thus save a lot of frustration when such predictions are checked beforehand.
We have preformed many such photo-resonance measurements. Several good resonances have been identified in various X-ray laser schemes.