Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The pentazenium cation (also known as pentanitrogen) is a positively charged homoleptic polynitrogen ion of the chemical formula N+ 5. Together with dinitrogen and azide anion, it is one of the only three polynitrogen species obtained in bulk quantities.Within High Energy Density Matter research program, ran by U.S. Air Force since 1986, systematic attempts to approach polynitrogen compounds began in 1998, when Air Force Research Laboratory at Edwards AFB became interested in researching alternatives to the highly toxic hydrazine-based rocket fuel and simultaneously funded several such proposals.