X-ray generation by friction of sticky tape

Professor S. Putterman (University of California, Los Angeles, USA) and his colleagues recently demonstrated that simply peeling ordinary sticky tape in a moderate vacuum can generate sufficient X-rays to take an image of a human finger. The phenomenon has long been known as tribo-luminescence (or mechano-luminescence), but their report (including online video accessible from the Nature News page) has impressed many. Nanosecond, 100-mW X-ray pulses as well as radio and visible light have been clearly confirmed to be correlated with stick-slip peeling events. They observed a 15-keV peak in X-ray energy spectra, and attempted to explain it by various models. For more information, see the paper, "Correlation between nanosecond X-ray flashes and stick-slip friction in peeling tape", C. G. Camara et al., Nature, 455, 1089-1092 (2008), and the news article, "Sticky tape generates X-rays - How weird is that?", Katharine Sanderson, Nature News, http://www.nature.com/news/2008/081022/full/news.2008.1185.html as well as readers' comments thereon. A very old and pioneering report describing how peeling tape can be a source of X-rays is "Investigation of electron emission on tearing away highpolymer film from glass in vacuum", V. Karasev et al., Doklady Akademii Nauk SSSR, 88, 777-780 (1953).