Molecular beam observations have been made of the radiofrequency spectra corresponding to reorientations of the deuteron, proton, and rotational magnetic moments in the HD molecule. For HD in the zeroth vibrational and first rotational state, these observations were made in magnetic fields of approximately 1700, 3400, and 4800 gauss. The results are found to be consistent with the theory of heteronuclear diatomic molecules. The direct result of these experiments is the determination of the Hamiltonian interaction constants: (1-crji)b/vd equals 0.773527 ±0.000016, c p is 85 600±18 cps, c d equals 13 122iU cps, di is 17 761±12 cps, d 2 equals 22 454±6 cps, and f/H 2 is (-26.90 ±0.40) X10 -6 cps gauss -2 . From these values of the interaction constants are derived the following physical quantities: the HD rotational magnetic moment KD O(JJ.J/J)I equals 0.663211 ±0.000014 nuclear magneton, the quadrupole moment Q of the deuteron is (2.738±0.014)X10~2 7 cm 2 , the rotational magnetic field B v ' at the proton is 19.879±0.006 gauss and H/ at the deuteron is 20.020±0.028 gauss, the internuclear spacing in the zeroth vibrational and first rotational state is such that HD o(i?~3)r* equals (0.74604±0.00010)X10~8 cm, and the dependence of the diamagnetic susceptibility on molecular orientation (£±i -£o) is -(3.56±0.20)X10~3 1 erg gauss -2 molecule -1 . Combining these values with Ramsey's theory on zero-point vibration and centrifugal stretching in molecules gives the high-frequency contribution to the molecular susceptibility, HD o(£ hf )i= (1.675±0.005) X10~3 1 erg gauss -2 molecule -1 ; the quadrupole moment of the electron distribution relative to the internuclear axis, HD o(&)i = (0.324±0.010)X10 -16 cm 2 ; and the high-frequency contribution to the magnetic shielding constant for HD, HD^hf)^ (-0.594±0.030)X10 -5 .

An electron-bombardment detector developed for the detection of noncondensable as well as condensable molecular beams is described. The ionization efficiency for a hydrogen deuteride beam is in the range of 10−5 to 10−4. Auxiliary components include: vacuum buffer chambers for source background gas reduction; a mass spectrometer for ion mass selection; an electron multiplier, electrometer, and phase-sensitive detector combination for signal observation. Modulation techniques for beam and magnetic resonance detection are discussed. Efficiencies, background problems, and relevant noise sources are included in a discussion of operational characteristics. A resonance line trace produced by at most 3% of a total HD beam is presented to demonstrate the signal to noise ratio at low signal levels. The system has effectively detected beams of permanent gases such as HD, D2, and Ne.