One of the long standing mysteries of Cold Fusion/LENR is the lack of gamma ray emmission. A nuclear reaction that changes the number of neutrons and protons in a nucleus to a more stable number will produce excess energy and, traditionally, there are two ways that this energy can be released:

• One or more particles moving at speed, such that the energy is released as kinetic energy
• One or more photons where the energy determines the frequency of the photon. The excess energy from nuclear reactions typically produce gamma ray photons.

The problem is that many reactions produce few if any photons, which is often been used as 'evidence' that there were no nuclear reactions taking place. However, it has been suggested that low energy nuclear reactions within so called 'condensed matter', a solid (or even a liquid) provide other options for getting rid of the excess energy.

Option 1: Photons are abosrbed within the lattice

One possibility is that photons are created, but they interact with the nearby atoms, and the energy is dumped into the lattice. In the simplest model this would heat the lattice up.

Mark Iverson has recently noted that there has been a recent paper that describes how a photon can travel through a lattice, repeatably interacting with the lattice and loosing energy.