Letter

Nature 455, 1089-1092 (23 October 2008) | doi:10.1038/nature07378; Received 30 December 2007; Accepted 27 August 2008

Correlation between nanosecond X-ray flashes and stick–slip friction in peeling tape

Carlos G. Camara1,2, Juan V. Escobar1,2, Jonathan R. Hird1 & Seth J. Putterman1

  1. Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, California 90095, USA
  2. These authors contributed equally to this work.

Correspondence to: Carlos G. Camara1,2Juan V. Escobar1,2 Correspondence and requests for materials should be addressed to C.C. (Email: camara@physics.ucla.edu) or J.E. (Email: escobar@physics.ucla.edu).

Relative motion between two contacting surfaces can produce visible light, called triboluminescence1. This concentration of diffuse mechanical energy into electromagnetic radiation has previously been observed to extend even to X-ray energies2. Here we report that peeling common adhesive tape in a moderate vacuum produces radio and visible emission3, 4, along with nanosecond, 100-mW X-ray pulses that are correlated with stick–slip peeling events. For the observed 15-keV peak in X-ray energy, various models5, 6 give a competing picture of the discharge process, with the length of the gap between the separating faces of the tape being 30 or 300 mum at the moment of emission. The intensity of X-ray triboluminescence allowed us to use it as a source for X-ray imaging. The limits on energies and flash widths that can be achieved are beyond current theories of tribology.

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