charged particle radiation delta ray Highly energetic electrons produced during inelastic collisions between ionizing radiation and atomic electrons. In a small proportion of collisions, the ejected electron receives a considerable amount of energy (i.e., >1,000 eV), allowing it to travel a delta electron delta electron Jack Miller NCRP Glossary (https://ncrponline.org/wp-content/themes/ncrp/PDFs/NCRP-Composite-Glossary.pdf) Delta ray energies increase with the velocity of the incident particle.