CERN Accelerating science

The fall of the antiproton into the nucleus

Photos of the lasers setup in ASACUSA

ASACUSA (continued)

What is laser spectroscopy ?

If you could look at the fall of the antiproton into the nucleus, you would see that is not "direct", but more like "descending a stair": it goes through the different "steps" defined by the energy levels of the atom. The study of the transitions between energy levels, that involve the absorption or emission of light, is called spectroscopy.

Now, one of the main goals of ASACUSA is to measure exactly the "height of each step", i.e. the energy between levels. One way to do it is to have the antiproton "jump" in a controlled way. How to convince it?

The principle of "laser spectroscopy" is to induce such jumps by a laser pulse. Only by tuning the laser "light" (= energy) to exactly the height of a step, the antiprotons can be made to jump. If one gets the jump, he will know the energy looking at the laser light which caused it!

ASACUSA physicists are planing to use, to this purpose, two beams of laser light and a pulsed beam of microwaves. With the latter, they hope to induce "mini-jumps" and reach the so called "hyperfine energy levels ".

Spectroscopic studies on the hydrogen atoms led to crucial understanding of matter and its components. In a similar way, the spectroscopy of "antiprotonic atoms" allows the study of the electrical and magnetic properties of the antiproton to extremely high precision, and permits to compare them with those of ordinary protons.

Several other detailed studies, both on the interactions of antiprotons with different materials and on the interactions of p-He+ with surrounding atoms and molecules, will be performed by ASACUSA in the next years.

If you whish to know more about the experiment, you can have a look at the ASACUSA pages.