Ch 6 Vocab
Discrete particle, or wave packets, of energy
Photon
Two waves that interact with one another and they form a greater intensity if they in the same phase
constructive interference
Why are atomic spectra (emission, absorption, and fluorescence) narrow?
Atomic spectra is narrow because atoms can only go through electronic transitions. They do not go through vibrational and rotational states. Atoms have very discrete and define energy levels.
Why are the sources for fluorescence and scattering instruments 90 degrees from the detector?
The source must be 90 degrees from the detector because it eliminates the possible interference of the detection. The source would create too much background noise and overwhelm the detector.
is the process by which a sample is vaporized and decomposed into atoms usually by heat.
atomization
atoms, molecules, or solids that are excited to high energy levels can decay to lower levels by emitting radiation (emission or luminescence) or through nonradiative processes
emission
when matter captures electromagnetic radiation and convert the energy of a photon to internal energy
absorption
Explain why molar absorptivity of a compound is dependent on wavelength.
Molar absorptivity: How well an analyte can absorb a wavelength under specific conditions.
Different wavelengths are absorbed by a compound under specific conditions
Why are IR sources not used for atomic absorption spectroscopy?
IR is not able to change the electronic state of an atom and atoms can only go between different electronic states. They are only able to vibrate or rotate molecules.
refers to the absorption of emitted radiation by unexcited atoms in the gas phase of a hollow-cathode lamp, flame, or plasma.
self-absorption
When radiation crosses an interface between media that differ in refractive index _______ occurs
reflection
When two waves that interact with one another form a cancel each other
destructive interference
Why do they not use X-rays to study chemical bonds?
X-rays exceed the energy that is needed to change transition states so it will end up breaking the bonds; they are used to study inner electrons. X-rays can do surface or elemental analysis
is encountered when the absorption or emission of a nonanalyte species overlaps a line being used for the determination of the analyte.
spectral interference
Why do electrothermal atomizers generally provide higher sensitivities than flame atomizers?
Electrothermal analyzers ensure that the sample is within the optical path for longer. This gives a better reading than a flame because a flame is destructive and fast towards the sample and the optical window is short.
Emission from triplet excited state
the electrons are oriented in the same way, it takes longer to come back to lower energy level
phosphorescence
Self propagating transverse oscillating wave of electric and magnetic field, The shorter the wavelength the higher the energy
electromagnetic radiation
What are some of the differences in the atomic and molecular absorption spectra and explain the observed differences?
Atomic spectra are going to be a very narrow and defined line spectra because they can only use electronic transitions. Molecular spectra are going to look like a band, because it can experience vibrational, rotational and electronic transitions states and the lines are so close together they form more of a band structure.
is the process in which gaseous cations bombard a cathode surface and eject atoms from the surface into the gas phase.
sputtering
Why are ionization interferences less severe in ICP than in flame emission spectroscopy?
The plasma itself ats as an ion suppressor
true continuum, photons being emitted are not due to quantized transitions so the spectra is continuous
Black body radiation
emission from singlet excited state
almost immediately comes back down to the lower energy level
fluorescence
Why does fluorescence emission have lower energy than the absorption spectra?
Fluorescence has lower energy because it loses some to nonradiative relaxation. It will lose some energy to kinetic energy by collision with other molecules. Stokes shift.
is a cation that preferentially reacts with a species that would otherwise react with the analyte to cause a chemical interference.
Why are atomic emission methods with an inductively coupled plasma (ICP) source better suited for multielement analysis than are flame atomic absorption techniques?
Since it is an emission technique so you could potentially measure all components at the same time as all elements are emitted at the same time vs absorption you have to have a source specific to the sample of interest.