Atomic Spectroscopy Vocab Flashcards
Absorption of radiation by atoms. The radiation is supplied by an external source.
Atomic Absorption
Re-emission of radiation by atoms from an excited state; emitted radiation is of longer wavelength than that of the initial absorption.
Atomic Fluorescence
Energy from some external process raises atoms into a spectroscopically excited state. The excited state atoms themselves then act as a source, re-emitting radiation as they decay back to the ground state.
Atomic Emission
typical narrow line source used in atomic absorption spectroscopy. Consists of a anode and cathode sealed in a glass tube at low pressure (<30 torr); the cathode is constructed of the atomic element of interest; a potential voltage difference between the anode and cathode causes the atoms in the cathode to become excited; return of the excited state atoms back to the ground state leads to emission of radiation and produces atomic line spectra specific for the cathode element.
Hollow Cathode Lamp
A relationship that describes the statistical distribution of a population of atoms or molecules in a set of energy levels m and n at thermal equilibrium
Boltzmann Distribution Law
The statistical likelihood, gm and gn, of particular energy states, e.g. m and n.
Degree of Degeneracy
The process of reducing a molecular sample into a population of its constituent
atoms by burning that sample in a flame
Flame Atomization
The process of converting a liquid sample into a fine spray mist of tiny droplets.
Nebulization
device that uses the flow of gas past the orifice of a capillary tube of small diameter; gas flow pulls the liquid from the capillary into the gas phase due to the reduced pressure (Venturi effect); surface tension of the liquid causes the column of liquid exiting the capillary to break apart into droplets.
Pneumatic Nebulizer
The process that evaporates the solvent leaving a solid/gas aerosol.
Desolvation
The process that vaporizes the aerosol gas leaving behind gaseous molecules.
Volatilization
The process that breaks down the gaseous molecules into its constituent atoms.
Atomization
An expression that relates the mean diameter of a nebulized droplet to: i) the viscosity of the analyte solution, ii) the density of the analyte solution, iii) the surface tension of the solvent, iv) the flow rate of the nebulizer gas, v) the flow rate of the aspirated solution, and vi) the velocity of the nebulizer gas.
Sauter Equation
Alternative to a pneumatic nebulizer that utilizes an ultrasonically driven crystal to vibrate the sample into droplets; tends to produce small, monodisperse droplet size distribution.
Ultrasonic Nebulizer
Alternative to flame atomization methods. consists of a cylindrical graphite tube equipped with optical windows at the ends; sample is added to the tube and dryed/ashed/atomized by electrical heating of the graphite tube to a final T ~3000 K.
Electrothermal / Graphite Furnace
Atomic spectroscopy background correction method using a continuum source (e.g. D2 lamp) in conjunction with a hollow cathode lamp line source; radiation from the HCL and D2 lamp is passes through a beam splitter or rotating chopper and the detector is synchronized such that it detects each signal separately,
Continuous Source Background Correction
Atomic spectroscopy background correction method using a strong magnetic field to split atomic energy levels; split components absorb polarized radiation from atomic transitions
Zeeman Background Correction
Atomic spectroscopy background correction method in which a magnetic field surrounds the sample and splits the sample atomic vapor into components
Analyte-Shifted Zeeman Background Correction
Atomic spectroscopy background correction method in which a magnetic field surrounds the source and splits the emission spectrum of the hollow cathode lamp source into components
Source-Shifted Zeeman Background Correction
Atomic spectroscopy background correction method using the properties of self-absorption or self-reversal behavior of hollow cathode lamps when operated at high current; high current with short pulse modulation (e.g. 500 mA, 0.3 ms) produces non-excited state atoms, quenching excited state species (background); low current (20 mA) produces total absorbance (background plus absorbance)
Smith-Hieftje / Source Self-Reversal Background Correction
Most common type of chemical interference in atomic spectroscopy where anions form compounds of low volatility and reduce the rate at which the analyte is atomized; typical for refractory oxide formation; these interferences can be reduced by using a fuel- rich flame to increase reducing species and restore free M atoms
Compound Formation Interferences
Type of chemical interference common in atomic spectroscopy at high T’s especially with O2 or N2O as oxidant; the ion M+ possesses a different electronic configuration than the neutral metal atom M and will interfere with the desired atomic absorption and emission processes; these interferences can be reduced by adding an ionization buffer (i.e. a more easily ionized species) to the sample to shift the ionization equilibrium away from M+.
Ionization Interferences
Type of chemical interference in atomic spectroscopy due to formation of strong complexes in solution that don’t readily dissociate at flame temperatures; these interferences can be reduced by forming competing complexes with analyte metal M that will more easily dissociate in flame, e.g. La3+, EDTA, or H+.
Condensed Phase Chemical Interferences
Type of interference in atomic spectroscopy due to unwanted absorption or emission from molecular species, or from closely overlapping spectral lines of two analytes; solutions include changing fuel gas, increasing T, using appropriate background correction, and decreasing the slit width.
Spectral Interferences
Type of interference in atomic spectroscopy due to scattering, rather than absorption, of particles in the flame that are roughly the same size as the wavelength of light; solutions include increasing T, using appropriate background correction, and decreasing the slit width
Light Scattering
Type of interference in atomic spectroscopy where the observed spectrum is negatively affected by sample constituents; usually worse for solid samples and can be severe in methods such as graphite furnace AA, DC arc, or AC spark sources; cause is usually variation of rate of sample volatilization; solutions include using closely matched standards at increase T.
Matrix Effects
An electrically conducting gaseous mixture containing a large concentration of cations and electrons with a net charge = 0; Ar is the usual gas used but O2 is also possible.
Plasma
Name given when the power supply used to energize the plasma is a radiofrequency induction coil.
Inductively Coupled Plasma (ICP)
Name given when the power supply used to initially energize the plasma is a direct current source.
Direct Current Plasma (DCP)
Name given when the power supply used to initially energize the plasma is a microwave generator.
Microwave-Induced Plasma (MIP)
Source for atomic emission spectrochemical analysis formed from graphite or metal electrodes a few mm apart; current (30 A, 200 V) is passed between these electrodes, causing high temperature (4000 – 5000 K) arcing and sample atomization.
Direct Current (DC) Arc
Source for atomic emission spectrochemical analysis formed from graphite or metal electrodes a few mm apart; typical operating conditions (10-50 kV , 1000 A instantaneous current) result in spark gap temperatures of 40,000 K.
Alternating Current (AC) Spark
