= Molecular beam electric resonance
The apparatus and dipole inference are described under <dipole evidence for bond polarization>. The <rigid rotor> supplies a general starting model for rotational <quantum states>; <rotational spectroscopy> measures their transition <frequencies>, while <molecular beam electric resonance> can select and analyze states through their <Stark effects>.
An actual implementation gives substance to the apparatus description above. In <Johannes Jacobus van Vaals>'s experiments, heated samples expanded with <argon> through a nozzle, then <molecular beam skimmers> formed the <molecular beam> in <vacuum>. Nonuniform <electric fields> selected and analyzed <quantum states>; parallel plates housed the <microwave> interaction. A <surface ionization detector> supplied <electric current> to an <electronic amplifier> and a <lock-in amplifier>. Resonant transfer into a rejected <quantum state> reduced the detected flux. <Phase locking> stabilized the <microwave> <frequencies>; an absorber suppressed reflections that could distort <spectral lines>. The thesis reports preliminary <electric dipole moment> components for gaseous <potassium cyanide> from measurements in nonzero <electric fields>. Such inference uses the <Stark effect>, rather than measuring <electronegativity>. The source notes restrictions from <electric-dipole selection rules> and <molecular beam> transit time; its preliminary dipole report is not a full calibration record. These are documented features of this apparatus, not proposed controls for the earlier <hydrogen chloride> experiment.<High Resolution Molecular Beam Study of Alkali Cyanides by Johannes Jacobus van Vaals>[chapter I §2, printed pp. 11–14: source, A/C/B fields, detector, phase locking, absorber and limitations; chapter III, printed p. 49, reference note 29: preliminary dipole components measured in nonzero fields]{ref}
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