Double-Pulse LIBS Molecular Emission Detection
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Solution Overview
Problem
Laser-Induced Breakdown Spectroscopy (LIBS) struggles to efficiently detect halogens like fluorine and chlorine due to their energy level distribution, particularly in the VUV spectral range, and lacks satisfactory detection limits for demanding applications, while also facing challenges in detecting rare-earth elements and boron.
Innovation Solution
The method employs a double-pulse LIBS system with Nd:YAG lasers, focusing on molecular emissions rather than ion line spectra, using molecules such as CaF, MgF, CaCl, and LaO to enhance detection sensitivity, particularly by delaying detection to capture long-lived molecular emissions after atomic and ion emissions have quenched.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional LIBS detects elements through ion line spectra, then the detection process is straightforward, but detection sensitivity for halogens and rare-earth elements is insufficient
Solution Approach 1:
The patent changes the detection parameter from ion line spectra to molecular emission spectra. By detecting molecular emissions (e.g., CaF, MgF, CaCl) instead of atomic ion lines, the system achieves significantly enhanced sensitivity for halogens and rare-earth elements, as molecular emissions provide stronger and more detectable signals for these elements
Solution Approach 2:
The patent introduces molecular emissions as an intermediary detection mechanism. Instead of directly detecting the element through its atomic ion lines, the system detects molecules formed during the plasma process (such as CaF for fluorine detection), which serve as intermediaries that provide enhanced detection capability
2Measurement precision
If detection is performed immediately after laser pulse, then atomic and ion emissions are captured, but molecular emissions are not sufficiently detected
Solution Approach 1:
The patent performs preliminary action by using a delay mechanism that allows atomic and ion emissions to quench before detection begins. The delay time (typically 1-100 microseconds) is optimized to let the plasma evolve from the initial atomic emission phase to the molecular emission phase, where molecules become the dominant emissive species
Solution Approach 2:
The patent employs periodic action through the use of delay time and gate width parameters in the detection system. By controlling the detection window to open after a specific delay and maintain it for a specific gate width, the system periodically captures molecular emissions at the optimal time when they are most intense and distinct from background noise
3Measurement precision
If single-pulse LIBS is used, then the system is simpler, but detection limits are not satisfactory for demanding applications
Solution Approach 1:
The patent applies segmentation by dividing the detection process into distinct temporal phases using delay time and gate width parameters. The detection window is segmented to capture molecular emissions specifically, separating them from the initial atomic emission phase. This temporal segmentation allows optimized detection of molecular species without requiring complex hardware modifications
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly increases detection sensitivity for halogens and rare-earth elements, achieving 100-200 times higher sensitivity for molecular emissions compared to ion detection, enabling the detection of low concentrations in various samples, including minerals and extraterrestrial materials.
Implementation Method 1
Laser-Induced Breakdown Spectroscopy (LIBS) uses optical emission spectra of atoms and atomic ions to analyze solid, liquid and gaseous samples. It offers ideal characteristics for real-time elemental analysis at atmospheric pressure
Implementation Method 2
LIBS uses optical emission spectra of atoms and atomic ions to analyze solid, liquid and gaseous samples. The emission of the elements in the plasma is measured
Data Source
AI summary
A method for detecting an element in a sample using molecular emission by double pulse laser-induced breakdown spectroscopy is provided. The method includes observing emissions from molecules including the element to be detected. The method is particularly useful for detecting halogens, whose elemental emissions are difficult to detect, rare earth elements and boron.