Scalar fields with a “ chameleon ” property , in which the effective particle mass is a function of its local environment , are common to many theories beyond the standard model and could be responsible for dark energy .
If these fields couple weakly to the photon , they could be detectable through the “ afterglow ” effect of photon-chameleon-photon transitions .
The ADMX experiment was used in the first chameleon search with a microwave cavity to set a new limit on scalar chameleon-photon coupling \beta _ { \gamma } excluding values between 2 \times 10 ^ { 9 } and 5 \times 10 ^ { 14 } for effective chameleon masses between 1.9510 and 1.9525 \mu eV .