An apparatus to generate negative hydrogen ions. The apparatus may include an ion source chamber having a gas inlet to receive H2 gas; a light source directing radiation into the ion source chamber to generate excited H2 molecules having an excited vibrational state from at least some of the H2 gas; a low energy electron source directing low energy electrons into the ion source chamber, wherein H− ions are generated from at least some of the excited H2 molecules; and an extraction assembly arranged to extract the H− ions from the ion source chamber.