Atomic spectrum is a spectrum consisting of a series of wavelengths of light emitted or absorbed by electrons in atoms when energy changes.atomic absorptionLight formation of partial wavelength in light sourceabsorption spectrum, is a dim stripe;launchphotonIs formed whenemission spectrum, are bright color stripes.two typesspectrumThey are not continuous, and the absorption spectrum fringe can correspond to the emission spectrum one by one.The spectrum of each atom is different, so it is called characteristic spectrum.[1]
The electrons in an atom can be in many different motion states, each of which has a certain energy. Under certain conditions, the number of atoms distributed in each energy level is certain, and most atoms are in the lowest energy state, that is, the ground state.When an atom is subjected to the external action of an arc or an electric spark, many atoms can transition from a lower energy state to a higher energy state, which is called an excited state.But the transition to high energy level EtwoThe atom of is unstable, about 10-8～10-5After S, it will jump to a low energy level EoneAnd the energy emitted is △ E=Etwo—EonePhotons of.According to the formula
The frequency of emitted photons can be obtained.[2]
If the negative film is used to receive this, a spectral line will be obtained.In fact, at the same time, there are other atoms that need to make transitions between other energy levels, and these transitions also need to emit light of other frequencies.These light with different frequencies are received, and bright spectral lines are obtained.This is calledAtomic emission spectrum。On the other hand, if a white light passes through a substance, the atoms in the substance will absorb light of some frequencies and transition from the low energy level to the high energy level.In this way, a series of dark stripes will appear after the white light passes through the material. The spectrum obtained in this way is called atomic absorption spectrum.Atomic emission spectrum and atomic absorption spectrum are collectively referred to as atomic spectrum.The intensity of each spectral line in the atomic spectrum is different from each other, and it is related to the transition probability between the corresponding two levels.
Atomic spectrum gives information about the distribution of energy levels in atoms and the transition probability between energy levels. It is a reflection of atomic structure and is determined by structure.There is a one-to-one internal relationship between spectrum and structure.Atomic spectroscopy is an important method for studying atomic structure, and can also be used for qualitative and quantitative analysis
correlation theory
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Atomic spectrum experiment
atomThe electromagnetic spectrum with a specific frequency that is emitted or absorbed when the movement state of an electron changes.Atomic spectrum is someLinear spectrum, the emission spectrum is some bright thin lines,Absorption spectrumThere are some hidden lines.AtomicEmission lineAndAbsorption linePrecise coincidence of positions.Different atoms have different spectra,Atomic hydrogen spectroscopyThe simplest is the spectrum of other atoms, and the most complex is the spectrum of iron atoms.useDispersion rateAnd larger resolutionSpectrographThe atomic spectrum also shows thatSpectral lineyesfine structure andHyperfine structureThe characteristics of all these atomic spectra reflect the regularity of the electronic motion inside the atom.
The basic theory of atomic spectrum isquantum mechanics。Atom according to its interiormotion state Can be in differentStationary state。Each certain state has a certain energy, which mainly includes the kinetic energy of the internal motion of the atomic system, the interaction energy between the nucleus and electrons, and the interaction energy between electrons.The lowest energy state is calledground stateThe energy higher than the ground state is calledexcited state, they constitute each part of the atomenergy level(SeeAtomic energy level）。High energy excited states cantransitionTo a lower energy statephotonOn the contrary, the lower energy state can absorb photons to transition to the higher excited state, and the frequencies of emitting or absorbing photons form the emission spectrum orAbsorption spectrum。Quantum mechanics theory can calculate the emission or absorption of atomic energy level transitionSpectral linePosition and intensity of spectral lines.
Role and research significance
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Complex atomic spectrum
Atomic spectroscopy provides abundant information about the internal structure of atoms.In fact, studying atomic structureAtomic physicsAnd quantum mechanics are established and developed in the process of studying, analyzing and clarifying atomic spectrum.Atoms are the components of matterBasic unit。The study of atomic spectrum is also of great significance for molecular structure and solid structure.The study of atomic spectrum plays an important role in the birth and development of the exciter, and the in-depth study of atomic spectrum will further promote the development of laser technology;In turn, laser technologyspectroscopyThe research provides an extremely effective means.Atomic spectrum technology is also widely used in chemistry, astrophysicsPlasma physicsAnd some applied technology disciplines.
Atomic or ionicmotion state Emitting or absorbing at a specific frequency when changes occurElectromagnetic spectrumThe atomic spectrum covers a wide range fromradio frequencySegment extends all the way toX-rayIn general, atomic spectrum refers to the spectrum in infrared, visible and ultraviolet regions
One of the atomic spectraSpectral lineThe generation of is related to the electron in a specific pair of atomsenergy levelBetweentransitionTherefore, atomic spectrum can be used to study atomic structure. Since atom is the basic unit of constituent matter, atomic spectrum is also very important for studying molecular structure, solid structure, etc. On the other hand, atomic spectrum can understand the movement state of atoms,In this way, we can study several physical processes including atoms. Atomic spectroscopy technology is widely used in chemistryAstrophysics, plasma physics and some applied technical sciences.
Technical classification
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As an important part of modern analysis and detection technology, atomic spectrum technology plays an important role in the field of analysis, and its development also reflects the continuous reform and innovation of analysis technology.The progress in research and application of atomic spectroscopy in China in the past 15 years (2000 – 2014) is reviewed.The content involves many branches of atomic spectrum, including atomic emission spectrum, atomic absorption spectrum,Atomic fluorescence spectrum, X-ray fluorescence spectrometry and atomic mass spectrometry.
Atomic Emission Spectrometry (AES):Atomic emission spectrometryIt is a method for qualitative, semi quantitative and quantitative analysis of elements according to the characteristic spectral lines emitted by atoms or ions of each chemical element when they return to the ground state from the excited state under thermal or electrical excitation.It is one of the earliest analytical methods in optical analysis, but it is also a relatively weak part in the research of atomic spectroscopy technology.
Atomic fluorescence spectroscopy (AFS): typical AFS detection process is to introduce samples by hydride/cold vapor generation, and argon hydrogen diffusionFlame atomizerRealize the atomization of the measured element, and free atoms areHollow cathode lampThe excited atomic fluorescence is received by the photomultiplier tube in a colorless light path to obtain the atomic fluorescence signal.In theory, AFS has both the advantages of AES and AAS, and also overcomes the disadvantages of both. However, due to the inherent defects of AFS, such as scattered light interference and serious fluorescence quenching, this method has high requirements for excitation light source and atomizer.
X-ray fluorescence spectrum (XRF): X-ray fluorescence spectrum can be divided into wavelength dispersion type (WD-XRF) and energy dispersion type (ED-XRF) according to the method of separating characteristic spectral lines.The difference between WD-XRF and ED-XRF is that the former uses a spectroscopic crystal to disperse the fluorescent beam, while the latter uses a high-resolution sensitive semiconductor detector andMultichannel analyzerThe obtained signal is separated according to the photon energy to determine the content of each element.
Atomic mass spectrometry (AMS): atomic mass spectrometry (AMS) is also calledInorganic mass spectrometryIt is a method of separating and detecting elements according to different mass charge ratios after atomizing the sample and using various ion sources to ionize it. It is widely used for qualitative and quantitative detection of elements in various samples.
