Early History of Mass Spectrometer Ionization Methods

Charles M. Judson
University of Kansas, Lawrence, KS, 66045

Gas Discharge

(1886) Goldstein discovered anode rays in a gas discharge. This method was used in the early mass analysis measurements of Wien (1898), Thomson (1912), and Aston (1919). In 1921, Aston extended this method to use a heated anode and then a composite anode made of a paste of powdered carbon mixed with sample. Later in 1936 Bainbridge loaded the sample into the base of the cathode. Much later (1971), Coburn and Kay used a glow discharge with the sample as a solid anode. The final chapter of gas discharge MS was ICP MS, one method for which was developed by Gray in 1983.

Vacuum Spark

(1935) Dempster used a vacuum spark with a new double focusing mass spectrograph to measure the isotopes of the noble metals, which had resisted previously available ionization methods. At the Metallurgical Lab during the war, Dempster used this instrument for chemical analysis, and reported this work in 1946. Shaw and Rall (1947) also described, without data, a Mattauch-Herzog photo plate instrument used at the Metallurgical Lab for SS analysis. Gorman, Jones and Hipple (1951) described use of a Dempster DF spectrometer with electronic recording of ratios to a beam monitor current. Hannay and Ahearn(1954) described a Mattauch-Herzog instrument for SS analysis using photo plate detection, which became the model for AEI and CEC SS instruments.

Surface Ionization

(1906) Gehrke and Reichenheim first produced anode rays by surface ionization. Dempster (1918), in his first experiment with his 180 degree spectrometer, used SI as the ionization method. In 1925 Kunsman used a sample mixed with iron oxide ammonia catalyst as a source for SI. Moon and Oliphant (1932) showed that atoms or ions bombarding a tungsten strip could provide a source for SI. After the war (1954) Inghram and Hayden reported that a 12 inch- 60 degree SI instrument had been developed, but a detailed description of this instrument is not easily found. Stevens(1952) described a vacuum lock for rapid introduction of SI samples. Inghram and Chupka (1953) described a multiple filament instrument with separate filaments for evaporation and ionization of the sample. Craig (1959) described an improved version of the multifilament SI source.

Electron Ionization

Most of Dempster's work from 1918 to 1935 used electron bombardment of heated solid samples as the ionization method. Smyth (1922) described the first mass spectrometer for electron ionization of gases and vapors, continuing to use Dempster's method of axial electrons with 180 degree analysis. Hogness and Lunn (1925) built a similar instrument, which Stewart and Olsen modified in 1931 to provide differential pumping of the filament in order to prove that the fragment ions of hydrocarbons were not thermal decomposition products. Bleakney (1929) described for the first time a 180 degree analyzer with a transverse electron beam, having the source and analyzer together in the field of a solenoid magnet. Tate, Smith and Vaughn (1935) built a larger solenoid instrument with differential pumping of the filament. Nier (1937) designed a 180 degree spectrometer with a conventional magnet, having a transverse electron beam collimated by the analyzer magnet. Then in 1940, Nier described a simple 60 degree sector analyzer with the same source, still with no focus plates and no cross-field focusing, and with no electron collimating magnet. Hipple, at Westinghouse in 1942 and Washburn, at CEC in 1943, both reported commercial mass spectrometers which had improved sources over the 1940 Nier design, but complete details of the sources were not immediately published. Finally in 1947 Nier described an instrument for precise isotope ratio measurements having a collimating magnet, focus plates, and cross-field focusing, which became the model for EI sources.

SIMS

(1931) Woodstock first observed secondary ion formation from bombarding ions. Herzog (1942) filed a German patent application for an SIMS analyzer. Herzog and Viebock (1949) briefly described an SIMS instrument based on Viebock's thesis. At RCA, Plumlee (1953) described a constructed SIMS instrument. Not the one proposed by Plummer, but one of a novel design with a very small ion gun using oscillating electrons, this instrument's source was within the field of the magnetic analyzer. Liebl and Herzog (1963) described a conventional SIMS source which was the basis for a commercial instrument manufactured by GCA. Castaign and Slodzian (1962) described an SIMS ion microscope which was later manufactured by Cameca. Liebl (1967) described a scanning microprobe SIMS which was manufactured by ARL. Benninghoven (1970) described a static SIMS instrument used for surface analysis. Magee, Harrington and Honig (1978) described a quadrupole SIMS for depth profiling. Barber et al. (1981-82) described fast atom bombardment of a sample in glycerol. Aberth and Burlingame (1982) showed that atom and ion bombardment of a sample in glycerol have the same result, and Burlingame proposed the term PID (particle induced desorption) for both cases.

Field Ionization

(1954) Inghram and Gomer first demonstrated field ionization from a point source based on work of Muller. Beckey (1958) used a wire emitter to demonstrate FI of organic compounds. Robertson and Viney (1966) used a blade emitter. Beckey (1969) used a heated wire to demonstrate field desorption. Aberth and Anbar (1968) demonstrated FI from a multipoint planar source.

Due to time and space limitations, other ionization methods such as chemical ionization and laser ionization have not been discussed here.