X-ray Emission
Vol 455 | 23 October 2008 | doi:10.1038/nature07378
L ETTERS
Correlation between nanosecond X-ray flashes and stick–slip friction in peeling tape
Carlos G. Camara1*, Juan V. Escobar1*, Jonathan R. Hird1 & Seth J. Putterman1
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 mm 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.
When a continuous medium is driven far from equilibrium, nonlinear processes can lead to strong concentrations in the energy density. Sonoluminescence7 provides an example in which acoustic energy concentrates by 12 orders of magnitude to generate subnanosecond flashes of ultraviolet radiation. Charge separation at contacting surfaces8,9 is another example of a process that funnels diffuse mechanical energy into high-energy emission. Lightning10, for instance, has been shown to generate X-rays with energies of more than 10 keV (ref. 11). Although triboelectrification is important in many natural and industrial processes, its physical explanation is still debated10,12. By peeling pressure-sensitive adhesive tape one realizes an everyday example of tribocharging and triboluminescence1: the emission of visible light. Tape provides a particularly interesting
L ETTERS
Correlation between nanosecond X-ray flashes and stick–slip friction in peeling tape
Carlos G. Camara1*, Juan V. Escobar1*, Jonathan R. Hird1 & Seth J. Putterman1
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 mm 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.
When a continuous medium is driven far from equilibrium, nonlinear processes can lead to strong concentrations in the energy density. Sonoluminescence7 provides an example in which acoustic energy concentrates by 12 orders of magnitude to generate subnanosecond flashes of ultraviolet radiation. Charge separation at contacting surfaces8,9 is another example of a process that funnels diffuse mechanical energy into high-energy emission. Lightning10, for instance, has been shown to generate X-rays with energies of more than 10 keV (ref. 11). Although triboelectrification is important in many natural and industrial processes, its physical explanation is still debated10,12. By peeling pressure-sensitive adhesive tape one realizes an everyday example of tribocharging and triboluminescence1: the emission of visible light. Tape provides a particularly interesting