Resonance-enhanced two-photon spectroscopy of magnetically trapped atomic hydrogen

We show that resonant enhanced two-photon spectroscopy is a very powerful a nd promising diagnostic method for trapped atomic hydrogen and antihydrogen . This method, in which photons of different wavelengths are used to excite H atoms from the 1S to the 3D or 3S level, uses the resonant enhancement o f the intermediate 2P level to obtain high sensitivity while at the same ti me offering potentially much higher spectral resolution than single photon (Lyman-alpha) excitation.