A pure rotational transition % MathType!MTEF!2!1!+- % feaagaart1ev2aaatCvAUfKttLearuqr1ngBPrgarmWu51MyVXgatC % vAUfeBSjuyZL2yd9gzLbvyNv2CaeHbd9wDYLwzYbItLDharyavP1wz % ZbItLDhis9wBH5garqqtubsr4rNCHbGeaGqiVu0Je9sqqrpepC0xbb % L8F4rqqrFfpeea0xe9Lq-Jc9vqaqpepm0xbba9pwe9Q8fs0-yqaqpe % pae9pg0FirpepeKkFr0xfr-xfr-xb9adbaqaaeGaciGaaiaabeqaam % aaeaqbaaGcbaWaaeWaaeaacqWGkbGsdaWgaaWcbaGaem4saS0aaSba % aWqaaiabdggaHbqabaWccqWGlbWsdaWgaaadbaGaem4yamgabeaaaS % qabaGccqGH9aqpcqaIXaqmdaWgaaWcbaGaeGymaeJaeGimaadabeaa % kiabgkHiTiabigdaXmaaBaaaleaacqaIWaamcqaIXaqmaeqaaaGcca % GLOaGaayzkaaaaaa!4AEA! $$ \left( {J_{K_a K_c } = 1_{10} - 1_{01} } \right) $$ of D2H+ is measured in the laboratory with a high-sensitivity submillimeter-wave spectrometer. The transition frequency is determined to be 691.660440(19) GHz with 1 σ in parentheses. The molecular constants for the ground state as well as the first excited vibrational states have been revised by refitting all available observed data.