[[abstract]]We report observation of the two-photon Doppler free 1S→2S transition in trapped atomic hydrogen. Because the atoms are confined at very low temperature, T-10 mK to 150 μK, motional averaging occurs and the line width is not limited by time-of-flight. We have observed sidebands in the resonance structure corresponding to the vibrational modes of the atom in the trap, with a typical fringe separation of 3 kHz. The spectral resolution is currently limited by laser jitter to about 2 kHz, corresponding to a fractional resolution of 2×10-12, but it is believed that the underlying structure is narrower. We are able to monitor the lifetime of atoms in the 2S state and have obtained values approaching the natural lifetime of 122 ms
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