14NO3 and 15NO3 were generated in a supersonic free jet, and their laser excitation spectra and dispersed laser induced fluorescence (LIF) spectra of the B∼2E′ – X∼2A2′ transitions from the vibrationless B∼2E′ state were observed. Because of the cooling of the gas in the supersonic jet, the observed spectra are with resolution an order of magnitude higher than those previously reported and allowed us to resolve, for example, the splitting between the a1′ and e′ components of the 2ν4 state. The spectra of 14NO3 and 15NO3 are similar but small isotope shift in the latter allowed us to separate the ν1 band from the 3ν4 (a1′) band which were overlapped in the former.The high resolution dispersed LIF spectra revealed panoramic views of the vibrational level structures in the X∼2A2′ ground electronic states of the two isotopomers. Although the accuracies of the measurement of energy levels are much less than those obtained from the direct high resolution infrared spectroscopy, the obtained patterns are more complete because totally symmetric (a1′) vibrations such as ν1,2ν2,2ν1,ν1 + 2ν2 etc. are also observed. Such clear and complete spectra have revealed remarkable ν4 progressions with detailed vibrational structures in the ground X∼2A2′ state. Near complete progressions of nν4 overtone bands, nν4 with n = 1 ∼ 5, ν1 + nν4 bands with n = 1 ∼ 4, some 2ν2 + nν4 and ν3 + nν4 have been assigned leaving few lines unassigned. There is no evidence of anomaly in the degenerate ν4 bending progression of the B∼2E′ – X∼2A2′ electronic transition of NO3.