I. Cycle averaged amplification and dampingConcerning the origin of equation ( 1) in the main text, and referring to figure 1, the respective scattering forces 1 are F c,a (v, i c,a ) = αi c,a f γ (∆ω c,a − kv) where i c,a is the cooling/amplification beam intensity at the ion position; ∆ω c,a ≡ ω c,a − ω o (ω o is the optical transition frequency); and α ≡ hkγ/2i sat (i sat is the saturation intensity of the dipole transition, and k = ω o /c). f γ (ω) is

An improved test of time dilation in special relativity has been performed using laser spectroscopy on fast ions at the heavy-ion storage-ring TSR in Heidelberg. The Doppler-shifted frequencies of a two-level transition in 7Li+ ions at v=0.064c have been measured in the forward and backward direction to an accuracy of Deltanu/nu=1 x 10(-9) using collinear saturation spectroscopy. The result confirms the relativistic Doppler formula and sets a new limit of 2.2 x 10(-7) for deviations from the time dilation factor gamma(SR)=(1-v2/c2)(-1/2).

We report the first observation of the laser-assisted photoelectric effect from a solid surface. By illuminating a Pt(111) sample simultaneously with ultrashort 1.6 eV and 42 eV pulses, we observe sidebands in the extreme ultraviolet photoemission spectrum. The magnitude of these sidebands as a function of time delay between the laser and extreme ultraviolet pulses represents a cross-correlation measurement of the extreme ultraviolet pulse. This effect promises to be useful to extend extreme ultraviolet pulse duration measurements to higher photon energies, as well as opening up femtosecond-to-attosecond time-scale electron dynamics in solid and surface-adsorbate systems.

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