Radiant energy – Electrically neutral molecular or atomic beam devices and...
Patent
1984-03-05
1986-02-11
Smith, Alfred E.
Radiant energy
Electrically neutral molecular or atomic beam devices and...
250288, H05H 302
Patent
active
045700664
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for producing molecular beams in which a test substance is transformed (vaporized) from a non-gaseous phase to a gaseous phase through the introduction of energy, the free molecules generated from the transformation of the test substance being mixed with a carrier gas and the carrier gas with the molecules of the test substance being cooled adiabatically through expansion in a beam of the carrier gas.
The invention relates further to an apparatus for accomplishing the above-mentioned method comprised of a gas beam jet for producing the beam of carrier gas, a device for introducing the carrier gas into the gas beam jet, an evaporator and mixing chamber for transforming a test substance from the nongaseous phase into the gaseous phase (vaporization), and for mixing this phase with the carrier gas, and an energy-producing device for introducing the energy for evaporation into the evaporator and mixing chamber.
A method and apparatus of this type well known, as is found for example, in the US-Z Chemical Physics Letters, Vol. 77, No. 3, Pages 448-451.
According to the present state of the art, desired molecular beams can be produced, which consist of a carrier gas, generally noble gas, for example, argon, and molecules mixed with the carrier gas inasmuch as these molecules are from a volatile substance which evaporates at a particular temperature at which the molecules definitely do not disintegrate, that is, insofar as thermally stable molecules are concerned.
In particular, according to the state of the art, molecular beams are produced by means of a method and an apparatus of the above-mentioned type which is well known only for thermally stable molecules. In this process, the molecule is evaporated or otherwise vaporized in a carrier gas atmosphere, for example, in an argon atmosphere, and after the formation of a molecular beam by means of a gas beam jet, the molecules are cooled through an adiabatic expansion, so that they thereby achieve a very low temperature, which is especially suitable for analysis by means of mass spectroscopy or other molecular or ionic investigation methods.
The evaporation of the molecules mixed in the carrier gas takes place in the above-mentioned evaporation and mixing chamber upstream of the gas beam jet in the chamber directly before the gas beam jet through which the mixture of the molecules to be analyzed and the carrier gas flows, and the gas beam is formed. This is effective inasmuch as the volatile substance which comprises the analyzed molecules or which the molecules contain is not automatically vaporized due to its vaporization pressure at room temperatures.
The preferred methods by means of which such molecular beams are analyzed are investigations by means of tuned laser beams either in fluorescent materials or by mass spectroscopic multi-photon ionization (MPI). The above-mentioned methods and apparatus for accomplishing these processes are not suitable for thermally unstable molecules; this is for nonvolatile molecules which disintegrate with heating before they have reached an adequate vaporization pressure.
For analysis of thermally unstable molecules, it has not been possible until now to produce molecular beams, but vaporization of such thermally unstable molecules has taken place directly in a vacuum, that is, without a carrier gas, whereby these thermally unstable molecules are more or less destroyed. In connection with the vaporization, there is produced an ionization and an analysis through ionization inspection methods as, for example, mass spectrometry methods.
For one such vaporization and ionization of thermally unstable molecules, there have been developed in recent times a series of methods by which these thermally unstable molecules are directly vaporized through ionization in a vacuum to be investigated by mass spectrometry. Some of the most important methods given here as examples are as follows: the spark discharge pyrolyzation, the spraying of a solution (electrospray) with immediate vaporization of the solution
REFERENCES:
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patent: 4259572 (1981-03-01), Brunnee et al.
Smalley et al, Accounts of Chemical Research, vol. 10, 1977, pp. 139-145.
Adams et al, Review of Scientific Instruments, vol. 52, No. 10, Oct. 1981, pp. 1469-1472.
Postumus et al, Analytical Chemistry, vol. 50, No. 7, Jun. 1978, pp. 985-991.
Cotter, Analytical Chemistry, vol. 52, No. 14, Dec. 1980, pp. 1589A-1606A.
Henke et al, Chemical Physics Letters, vol. 77, No. 3, Feb. 1981, pp. 448-451.
Fung et al, Z. Naturforsch, vol. 36a, 1981, pp. 1338-1339.
Hays et al, Z. Naturforsch, vol. 35a, 1980, pp. 1429-1430.
Schlag Edward W.
Selzle Heinrich
von Weyssenhoff Hanns
Berman Jack I.
Smith Alfred E.
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