Atomic absorption spectroscopy

Claim 3

A method as claimed in claim 1 comprising the steps of modulating said resonance line of the illuminating radiation and determining the intensity of similarly modulated resonance radiation reemitted by the cloud.

Claim 4

A method as claimed in claim 2 wherein said resonance line is one of a plurality of resonance lines in the illuminating radiation, said plurality of resonance lines being respectively characteristic of a plurality of elements to be determined, the method including the steps of modulating said resonance lines in respective distinctive manners, and determining the intensity of resonance radiation reemitted by the cloud and modulated in any one of said distinctive manners.

Claim 5

Apparatus for use in atomic absorption spectroscopic analysis comprising a vacuum chamber, means for mounting a sample of a substance within the chamber, means for creating a pulsed discharge to cause sputtering of the sample so that an atomic vapor of the substance is produced in the chamber, means for illuminating said vapor with illuminating radiation comprising a resonance line characteristic of an element to be determined, photodetecting indicator means arranged to receive resonance radiation reemitted by said vapor in a direction such that illuminating radiation is not received and to indicate the concentration of said element in the sample in response to received resonance radiation, and means to render the photodetecting indicator means ineffective during each discharge pulse.

Claim 6

Apparatus for use in atomic absorption spectroscopic analysis comprising a vacuum chamber, means for mounting a sample of a substance within the chamber, means for creating a pulsed discharge to cause sputtering of the sample so that an atomic vapor of the substance is produced in the chamber, means for illuminating said vapor with illuminating radiation comprising a resonance line characteristic of an element to be determined, photodetecting indicator means arranged to receive resonance radiation reemitted by said vapor in a direction such that illuminating radiation is not received and to indicate the concentration of said element in the sample in response to received resonance radiation, and means to render the photodetecting indicator means ineffective during each discharge pulse.

Claim 7

Apparatus as claimed in claim 4 comprising means to modulate said resonance line of the illuminating radiation, the photodetecting indicator means being responsive to similarly modulated resonance radiation reemitted by the vapor.

Claim 8

Apparatus as claimed in claim 5, wherein said resonance line is one of a plurality of resonance lines being respectively characteristic of a plurality of elements and means for modulating said plurality of lines in respective distinctive manners, and the photodetecting indicator means being responsive to resonance radiation reemitted by the vapor and modulated in any of said distinctive manners so that said plurality of elements can be determined simultaneously.

Claim 9

Apparatus as claimed in claim 6 wherein the means for illuminating the vapor comprises a plurality of sources arranged to produce respective resonance lines modulated in respective distinctive manners, and the photodetecting indicator means comprises a photodetector arranged to supply a signal representing received radiation to a plurality of indicator means selects from said signal a component representing resonance radiation modulated in a similar manner to the resonance line emitted by its respective source. 8 Apparatus for use in atomic absorption spectroscopic analysis comprising wall means defining a sealable chamber, a projection extending from the wall means into the chamber and arranged to receive a sample of a solid substance at a location spaced from the wall means, an electrode within said chamber enabling application of an electrical potential difference between the electrode and the sample so that a discharge can be created between them to cause sputtering of the sample thereby to create in the region of said location a cloud of atomic vapor of the sample under such conditions that if the sample contains a particular element the cloud will absorb and reemit resonance radiation characteristic of that element, a pair of windows in said wall means facing each other from opposite sides of said region, an atomic spectral lamp located outside the CHAMBER for producing resonance line radiation characteristic of said particular element to illuminate said cloud with a beam of radiation which enters the chamber by way of one window of the pair and leaves by way of the other, and a further window in the wall means so located relative to said pair of windows that in use the beam does not impinge on it but resonance line radiation absorbed and reemitted by the cloud is permitted to leave the chamber via said further window to be received by photodetector means responsive thereto and located outside the chamber.

Claim 10

Apparatus as claimed in claim 8 and further including energizing means for generating said electrical potential difference such that in use a pulsating discharge is produced, and means to render the photodetector means ineffective during each discharge pulse.

Claim 11

Apparatus as claimed in claim 8 and further comprising gas inlet means and outlet means extending through said wall means to permit forced circulation of rare gas through the chamber in use.

Claim 12

Apparatus as claimed in claim 8 and further comprising a sleeve of insulating material located around the projection but spaced therefrom and operative to localize the discharge on the sample.

Claim 13

Apparatus as claimed in claim 8 wherein the photodetector means comprises a photomultiplier having peak sensitivity to radiation near the ultraviolet region of the spectrum.

Claim 14

Apparatus as claimed in claim 8 wherein means is provided to enable force-cooling of the projection in use.

Claim 15

Apparatus as claimed in claim 13 wherein the projection is hollow and extends through the wall means, and said means to enable force-cooling is located within the hollow projection.

Claim 16

Apparatus as claimed in claim 8 wherein said resonance line is one of a plurality of resonance lines in the illuminating radiation, the plurality of resonance lines being respectively characteristic of a plurality of elements and being modulated in respective distinctive manners, and the photodetector means being responsive to resonance radiation reemitted by the vapor and modulated in any of said distinctive manners so that said plurality of elements can be determined simultaneously.

Claim 17

Apparatus for use in atomic absorption spectrophotometric analysis of a sample for a plurality of atomic species comprising means for creating a cloud of atomic vapor from the sample under such conditions that if the sample contains any one of said species the cloud can absorb and reemit resonance radiation characteristic of that species against a background of emissive radiation at wavelengths other than that of the resonance radiation, means to generate illuminating radiation to illuminate the cloud and containing a plurality of resonance lines respectively characteristic of said plurality of species and modulated in respective distinctive manners, photodetector means having peak sensitivity in the ultraviolet region of the electromagnetic spectrum and arranged to receive, and produce an output signal representative of, resonance radiation reemitted by the cloud in a direction such that none of said illuminating radiation is received directly, and demodulator means responsive to the output signal and arranged to select therefrom components modulated in any of said distinctive manners and respectively representative of the concentrations in the sample of the species represented by the corresponding modulated resonance lines in the illuminating radiation.

Claim 18

Apparatus for use in atomic absorption spectrophotometric analysis of a sample for a plurality of atomic species comprising means for creating a cloud of atomic vapor from the sample under such conditions that if the sample contains any one of said species the cloud can absorb and reemit resonance radiation characteristic of that species against a background of emissive radiation at wavelengths other than that of the resonance radiation, means to generate illuminating radiation to illuminate the cloud and containing a plurality of resonance lines respectively characteristic of said plurality of species and modulated in respective distinctive manners, photodetector means having peak sensitivity in the ultraviolet region of the electromagnetic spectrum and arranged to receive, and produce an output signal representative of, resonance radiation reemitted by the cloud in a direction such that none of said illuminating radiation is received directly, and demodulator means responsive to the output signal and arranged to select therefrom components modulated in any of said distinctive manners and respectively representative of the concentrations in the sample of the species represented by the corresponding modulated resonance lines in the illuminating radiation.

Claim 19

Apparatus as claimed in claim 16 wherein the means to generate the illuminating radiation comprises a plurality of sources of radiation arranged to generate respective ones of said resonance lines and to illuminate the cloud in a predetermined sequence, the demodulator means being arranged to switch the output signal of the photodetector means between a plurality of output means in a corresponding sequence so that said components are received by respective ones of said output means.

Claim 20

Apparatus as claimed in claim 17 whErein the resonance lines are additionally amplitude modulated at a preset frequency, and the demodulator means is selectively responsive to that frequency.

Claim 21

Apparatus as claimed in claim 16 wherein the means to generate the illuminating radiation is arranged to modulate said resonance lines at respective distinctive frequencies and the demodulator means comprises a plurality of demodulator output means selectively responsive to respective ones of said frequencies.