Rotational spectra in the v = 0, 1, 2, and 3 levels of the ground (1Σ) state of sodium hydride have been observed using tunable far-infrared radiation generated from the difference frequency between two CO2 lasers. The Dunham coefficients, which have been determined without the use of optical data or isotopic scaling relations, are Y01 = 146 999.138(38) MHz, Y02 = -10.29481(54) MHz, Y03 = 6.243(49) × 10-4 MHz, Y11 = -4109.912(68) MHz, Y12 = 0.14695(68) MHz, Y21 = 33.341(34) MHz, Y22 = -2.69(20) × 10-3 MHz, and Y31 = -1.0517(55) MHz. The constants are typically an order of magnitude more accurate than the best values previously available, and where comparison is possible, agreement is found to be excellent.
Bibliographical noteFunding Information:
’ Work supportedin part by NASA Contract W-15,047. * National Research Council Postdoctoral Fellow.