A measurement of the mass fluctuation spectrum from the cluster X-ray temperature function

We present a statistically complete sample of galaxy clusters which also has complete X-ray temperature information. Using this sample we derive the cluster bolometric luminosity and temperature functions. The temperature function constrains the shape and amplitude of the mass fluctuation power spectrum. For a power law, i. e. , with the fluctuation power spectrum proportional to kⁿ^, we find n = - (1. 7^+0. 65^_-0. 35_), and an amplitude which implies that the rms value of δM/M is 0. 59 +/- 0. 02 on a scale of 8 h^-1^ Mpc at the present epoch.