AbstractRoom temperature phosphorescence (RTP) of aromatic hydrocarbons has been investigated in deoxgenated SDS micelles and in the presence of a hydrophobic heavy‐atom containing species. No RTP was observed in spherical or sub‐rodlike micelles. In the presence of a heavy‐atom containing species, a tremendous increase in phosphorescence intensity was observed during the sphere‐to‐rod transition induced by the addition of a strong electrolyte. The increased microviscosity and the incorporation of more heavy atoms during the micellar elongation will lead to an increase in the rate of intersystem crossing and a decrease in the rates of nonradiative processes, favoring the observation of RTP. At high temperatures, the phosphorescence intensity is reduced dramatically probably because of the decrease in rigidity and aggregation number of the micelle with less heavy atoms incorporated. Various heavy‐atom containing species induce RTP to a different extent. Iodoethane exhibits the most prominent heavy atom effect. 1,2‐Dibromoethane, 1‐bromopropane, and bromobenzene are about 40% as efficient as iodoethane in inducing RTP, while long‐chain 1‐bromoalkanes and polar species are much less efficient. This study demonstrates the feasibility of detecting RTP in deoxygenated SDS rodlike micelles using a suitable hydrophobic heavy‐at