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A portion of a typical quadratic array for a rare-earth atom, with columns representing upper energy levels and rows representing lower levels. Obtaining such an array for as many lines as possible represents a first step in an analysis of the spectrum.
The spectrum interval sorter (background) with the magnetic punch for producing wave number tapes (foreground). Any desired length of loop can be accommodated between the upper and lower tape sections, to provide for recording intervals in any desired wave number range.
Short section of 35-mm paper strip punched with round holes for fiducial marks and rectangular holes for the wave numbers of spectrum lines. Light passing through superposed holes as the tape sections pass through the sorter records wave number intervals on photographic paper.
Small section of a typical record from the interval sorter, in which wave number differences appear plotted horizontally against wave numbers vertically.
Optical principle of the interval recorder, in which light passes through pairs of holes having the pre-set wave number interval, to fire a strobolamp and record the corresponding wave numbers.
Short section of a film record from the interval recorder.
A section of the plate-track of the 10-meter grating of the M.I.T. Spectroscopy Laboratory.
Small section of a spectrogram from the 10-meter grating.
Short section of a record from the automatic comparator, with wave-lengths automatically recorded on a density trace of the spectrogram.
The Bitter 1700-kw electromagnet giving 100,000-oersted magnetic fields, with water-cooled arc in place.
Sections of typical records of Zeeman patterns made with the automatic comparator.
The Winmac, arranged for the automatic reduction of Fabry-Perot spectrograms with electronic fringe location.
A portion of the Michelson ruling engine at M.I.T. The scale is indicated by the fact that the screw is 3.5 inches in diameter.
Diagram showing the mode of illumination of an echelle.
Measured intensity distribution of Hg 5461 in various orders of an echelle between 393 and 404.
A portion of the iron spectrum between 3600 and 4400A as obtained by crossing a Bausch and Lomb echelle with a quarto Littrow spectrograph. Several vertical echelle cycles are shown, and the orders used vary from the 570th at one end of the plate to the 695th at the other. The horizontal streak arises from light directly reflected from the back of the prism, which serves as a fiducial mark.