single molecule imaging.

At the x-ray energies required to reach atomic resolution ($\sim$ 10 keV), Compton scattering becomes another significant source of background scattering[@Slowick2014]. The background is predicted to depend on the magnitude of $q$, and would increase the noise level $\sigma_N$ by adding to the right hand side of Eq. . It has been predicted that for for beam intensities currently available at hard x-ray energies, the Compton background only becomes significant at resolutions greater than 2 Å[@Slowick2014]. Hence, Compton scattering is not expected to significantly influence the results presented here.

Conclusion
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We have analyzed shot-to-shot damage-noise fluctuations for single molecule diffraction. For spatially uncorrelated damage processes, there is a clear damage gating effect by which longer pulses measure the same average diffraction contrast as shorter pulses with the same intensity. The results further suggest that pulse energy is more important than pulse duration for maximizing signal to noise for these damage processes. In other words, a pulse 30 fs in duration may be preferable to a sub 5 fs pulse, if the later has an order of magnitude less pulse energy. If both 30 fs and 5 fs pulses have same pulse energy, then the shorter pulse 