The Breit-Wheeler process (convert two photons into electron+positron) has been one of the most elusive fundamental processes in electromagnetism. This prediction came when quantum mechanics was first being developed in the early 1930s but was not observed for more than 80 years after its prediction, since high energy photons are hard to come by. In contrast, many of the other fundamental processes were discovered fairly quickly after their predictions (the photo electric effect was discovered even before its quantum interpretation was given by Einstein, for which he won the nobel prize)
What’s the difference between photons coming off the gold ion traveling at 0.995c vs a high energy photon with a high frequency like a gamma ray? Like can’t you shoot 2 beams of gamma rays at each other and have matter anti matter pairs pop up?
The difference is you effectively control the path of the photons coming off the gold ion due to that 0.995c and the ion itself being in a focused beam which depends on its charge. The photon is projected forward in the direction of travel.
Gamma beams are hard to come by. How are you going to make two focused, directional gamma beams pointing accurately at each other?