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H2O -- an asymmetric rotor. (see its wikipedia entry)

Basic information

Boiling temperature: 100 C (= 373.15K)
Solidify temperature: 0 C (= 273.15K)
Dipole moment: 1.8546 D.
 Isotopic species detected in space: HDO, D₂O.
Most observed H2O maser lines: 22.23508 GHz (J,Ka,Kc = 616-523)
 All possibly strong H2O lines (MHz) from JPL linelist (w\ E_low < 600 cm^-1 & nu < 4 THz )
(Notes: ortho: ??; para: ??; metastable: ??)

• (< 100 GHz): 22235.0800;
• (< 1 THz): 183310.1170; 325152.9190; 380197.3720; 448001.0750; 474689.1270; 488491.1330;
                   556936.0020; 620700.8070; 752033.2270; 916171.5820; 970315.0220; 987926.7640;
• (< 2 THz): 1097364.7910; 1113342.9640; 1153126.8220; 1162911.5930; 1207638.7140; 1228788.7720; 1322064.8030;
                   1410618.0740; 1602219.1820; 1661007.6370; 1669904.7750; 1713882.9730; 1716769.6330; 1716957.0490;
                   1794788.9530; 1867748.5940; 1880753.0020; 1893686.5103; 1918485.3240; 1919359.5310;
• (< 3 THz): 2014864.9483; 2040476.8100; 2074432.3050; 2164131.9800; 2196345.7560; 2221750.5000; 2264149.6500;
                   2365899.6590; 2391572.6280; 2462933.0320; 2630959.5200; 2640473.8360; 2657665.7900; 2685638.9690;
                   2773976.5880; 2880025.3690; 2884278.9400; 2962111.0940; 2968748.6540; 2970800.2440;
• (< 4 THz): 3013199.5660; 3043766.1490; 3126585.0700; 3135010.9510; 3165532.7340;
                   3167578.2370; 3182186.8480; 3331458.3760; 3536666.8070; 3599641.7080;
                   3654603.2820; 3691315.5500; 3798281.6380; 3807258.4120; 3977046.4810;
  

Observations

• (from Sunada et al., 2007PASJ...59.1185S)
  Facts: They surveyed the H2O maser (J,Ka,Kc) = (6,1,6)-(5,2,3) line and 3 NH3 lines (simultaneously) in a sample of cool IRAS sources in the Galaxy with strong CO emission using the Nobeyama 45-m telescope. Beamwidth is 73", pointing accuracy of 8", 1024-channel AOS with bandwidth of 40 MHz and spectral resolution of 37 kHz (~0.5 km/s) . The survey sensitivity is: T*A(rms) = 0.1K, or rms = 0.24 Jy, integration time = 5 min.
  Conclusions: They did 2229 observations towards 1563 sources, detected H2O masers in 222 sources, with 75 of them are new.