An astronomer researching exoplanets.^[ref]

An astronomer studying the Milky Way centre.^[ref]

An astronomer studying the Milky Way centre.^[ref]

An astronomer studying the Milky Way centre.^[ref]

An astronomer researching exoplanets.^[ref]

An astronomer researching radio astronomy.^[ref]

An astronomer who designed astronomical spectrographs, including ELODIE.^[ref]

An astronomer.^[ref]

An astronomer.^[ref]

A chosen boundary in a frequency response, commonly where the voltage amplitude gain falls to $1/\sqrt{2}$ of its pass-region value. The convention must specify the reference gain.

For a linear time-invariant system, a sinusoidal wanted signal at ${\omega }_s$ and an unwanted sinusoidal component at ${\omega }_n$ acquire their separate frequency response factors. The ratio of their output amplitudes, divided by their input amplitude ratio, is $\eta =|H({\omega }_n)|/|H({\omega }_s)|$. An amplitude attenuation factor of $F=1/\eta$ corresponds to a factor $F^2$ in squared-amplitude power ratios under a common impedance convention. The unwanted component's own absolute attenuation is $|H({\omega }_n)|$, which need not equal its attenuation relative to the wanted signal.

Cited experimental account: Figures 70–77.

Chapter IV; inspected §§70–75.

Chapter III, pp. 119–155; inspected §§61–64.

In 1947, Willis Eugene Lamb Jr. and Robert Curtis Retherford dissociated hydrogen in a tungsten oven, crossed its atomic jet with electrons for collisional excitation, and detected surviving $2S$ atoms by electron ejection from metal. An electrometer and galvanometer read the current. They interrupted fixed-frequency microwaves while sweeping the static magnetic field; a flip coil calibrated the field. Their Zeeman splitting comparison placed $2S_{1/2}$ about $1000$ $\mathrm{MHz}$ above $2P_{1/2}$; the plotted $1000$ $\mathrm{MHz}$ displacement was explicitly not a best fit.^[ref]

The 1955 lecture's apparatus cross-section identifies movable slits, an electron bombarder, a radiofrequency transmission line with beam slots, a d.c. quenching electrode, metal target, electron collector, and magnet poles. A $2S\to 2P$ transition followed by rapid spontaneous emission leaves a ground-state atom unable to eject detector electrons. The scan holds radiofrequency and amplitude fixed. Natural linewidth and unresolved hyperfine structure broaden resonances, whose analysis yields zero-field separations.^[ref]

Static electric field quenching supplied a control. The 1947 report identifies natural linewidth, hyperfine structure, excessive microwave intensity, and field inhomogeneity as width contributions, and flags imperfect magnetic calibration. It does not specify an absolute microwave-frequency calibration procedure.^[ref]

The surname is Robert Curtis Retherford's: “Retherford” and “Rutherford” name different people. The historical Lamb-Retherford experiment should retain the former spelling.^[ref]