Article on Cherenkov Radiation

["Jacobus, John (OD/ORS)" <jacobusj@ors.od.nih.gov>]

Cherenkov Radiation at Speeds Below the Light Threshold: Phonon-Assisted
Phase Matching 
T. E. Stevens,12* J. K. Wahlstrand,1 J. Kuhl,2 R. Merlin1 

Science 2001 January 26; 291: 627-630

Charged particles traveling through matter at speeds larger than the phase
velocity of light in the medium emit Cherenkov radiation. Calculations
reveal that a given angle of the radiation conical wavefront is associated
with two velocities, one above and one below a certain speed threshold.
Emission at subluminal but not superluminal speeds is predicted and verified
experimentally for relativistic dipoles generated with an optical method
based on subpicosecond pulses moving in a nonlinear medium. The dipolar
Cherenkov field, in the range of infrared-active phonons, is identical to
that of phonon polaritons produced by impulsive laser excitation. 

1 The Harrison M. Randall Laboratory of Physics, University of Michigan, Ann
Arbor, MI 48109-1120, USA. 
2 Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany. 
*   Present address: Veridian ERIM International, Post Office Box 134008,
Ann Arbor, MI 48113-4008, USA

-- John 
John Jacobus, MS, CHP
Health Physicist 
3050 Traymore Lane
Bowie, MD  20715-2024

E-mail:  jenday1@email.msn.com (H)      
************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html