Action spectrum for the Inactivation of Viruses. 
Lytle, C. D., and J.-L. Sagripanti, Predicted Inactivation of Viruses of Relevance to Biodefense by Solar Radiation, Journal of Virology, Nov. 2005, p. 14244-14252, doi:10.1128/JVI.79.22.14244-14252.2005.  Data from their figure 1.
Wavelength    Response
254.	      1.00
280.	      0.7
285.	      .45
289.	      .4
290.	      .2
296.5	      .1
301.5	      .02 
305.	      .015
310.	      8.e-4
313.	      4.5e-4
315.	      2.e-4
320.	      1.1e-4