Laser-triggered plasma apparatus for atomic emission spectroscopy
First Claim
1. A method for analyzing composition of a sample with an optical spectroscopic instrument, the sample characterized by a threshold ablation energy per unit area with respect to the instrument, and by a surface at an interface between the sample and a gas, the method comprising:
- a. creating a plasma at a specified location in the gas proximate to an area at the surface of the sample by application of a first electromagnetic field characterized by a first spectral range and a second electromagnetic field characterized by a second spectral range, wherein at least one of the first and second electromagnetic fields is applied in a pulse of energy per unit area less than the threshold ablation energy; and
b. detecting resonant emission emitted by atoms of the sample vaporized into the plasma.
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Abstract
Multiple energy sources, such as a laser and electrical current, are employed, in close coordination, spatially and temporally, to clean a sample, vaporize its material and excite vapor atoms for the purpose of atomic emission spectroscopy. These methods permit better monitoring and control of the individual processes in real time, lead to higher consistency and higher quality optical emission spectra, and enhance the measurements of non-conducting solids, liquids and gases. Additionally, a portable instrument is provided with both laser source and spectrometer optically coupled to a hand-holdable unit.
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Citations
21 Claims
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1. A method for analyzing composition of a sample with an optical spectroscopic instrument, the sample characterized by a threshold ablation energy per unit area with respect to the instrument, and by a surface at an interface between the sample and a gas, the method comprising:
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a. creating a plasma at a specified location in the gas proximate to an area at the surface of the sample by application of a first electromagnetic field characterized by a first spectral range and a second electromagnetic field characterized by a second spectral range, wherein at least one of the first and second electromagnetic fields is applied in a pulse of energy per unit area less than the threshold ablation energy; and b. detecting resonant emission emitted by atoms of the sample vaporized into the plasma. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method for analyzing composition of a sample with an optical spectroscopic instrument, the sample characterized by a surface at an interface between the sample and a gas, the method comprising:
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a. applying an non-ionizing electrical bias field across a volume of the gas proximate to an area at the surface; b. triggering creation of a plasma at a specified location within the volume by application of an optical pulse; and c. detecting resonant emission emitted by atoms of the sample vaporized into the plasma. - View Dependent Claims (17, 18)
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19. A portable apparatus for analyzing composition of a sample characterized by a threshold ablation energy and by a surface at an interface between the sample and a gas, the apparatus comprising:
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a. a hand-holdable unit for conducting spectrometric analysis in close proximity to the sample; b. a laser optically coupled to the hand-holdable unit for providing pulses of optical energy; c. an optical element disposed entirely within the hand-holdable unit for focusing the optical energy to create a plasma at a controlled location in a proximity of the sample; d. an electrode structure coupled to the hand-holdable unit for sustaining a discharge within the plasma; e. a spectrometer optically coupled to the hand-holdable unit for dispersing resonant emission emitted by atoms onto at least one detector; and f. a processor for receiving a signal from the at least one detector and determining, therefrom, a characteristic of the sample. - View Dependent Claims (20, 21)
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Specification