▁ 2 H ▁( de uter ium ). ▁Its ▁proper ▁mole cular ▁formula ▁is ▁H 2 H , ▁but ▁for ▁simpl ification , ▁it ▁is ▁usually ▁written ▁as ▁HD . ▁ ▁Pre par ation ▁and ▁ ▁occurrence ▁In ▁the ▁labor atory ▁it ▁is ▁produced ▁by ▁tre ating ▁sod ium ▁hyd ride ▁with ▁de uter ated ▁water : ▁Na H ▁ ▁+ ▁ ▁D 2 O ▁▁ ▁→ ▁ ▁HD ▁ ▁+ ▁ ▁Na OD ▁ ▁H ydro gen ▁de uter ide ▁is ▁a ▁minor ▁component ▁of ▁naturally ▁occurr ing ▁mole cular ▁hydro gen . ▁It ▁is ▁one ▁of ▁the ▁minor ▁but ▁notice able ▁components ▁of ▁the ▁atmos pher es ▁of ▁all ▁the ▁giant ▁plan ets , ▁with ▁abund ances ▁from ▁about ▁ 3 0 ▁p pm ▁to ▁about ▁ 2 0 0 ▁p pm . ▁HD ▁has ▁also ▁been ▁found ▁in ▁super n ova ▁rem n ants , ▁and ▁other ▁sources . ▁ ▁Radio ▁emission ▁spect ra ▁ ▁HD ▁and ▁H 2 ▁have ▁very ▁similar ▁emission ▁spect ra , ▁but ▁the ▁emission ▁frequencies ▁differ . ▁ ▁The ▁frequency ▁of ▁the ▁astronom ically ▁important ▁J ▁= ▁ 1 - 0 ▁rot ational ▁transition ▁of ▁HD ▁at ▁ 2 . 7 ▁TH z ▁has ▁been ▁measured ▁with ▁tun able ▁F IR ▁radiation ▁with ▁an ▁accuracy ▁of ▁ 1 5 0   k Hz . ▁ ▁References ▁ ▁Further ▁reading ▁Sp itzer ▁observations ▁of ▁hydro gen ▁de uter ide ▁ ▁Category : H ydro gen ▁Category : H ydro gen ▁comp ounds ▁Category : De uter