Chapter 6 Flashcards by Jillian Mulholland

The angle of the cone of light exiting a sample observed by microscopy

Angle aperture (AA)

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Materials that have more than one refractive index

Anisotropic

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Scattering interactions that start from an excited state; a type of inelastic scattering

Anti-Stokes scattering

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An opening, often adjustable, that determines how much light or electromagnetic energy passes through; usually designed to limit stray light

Aperture

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Ionization using an electrical discharge used for LCMS instrumentation and some IMS instrumentation

Atmospheric pressure chemical ionization (APCI)

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Generically, the width of a band of electromagnetic energy measured in terms of wavelength

Bandwidth

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In a spectrum, chromatogram, or other peak-based output, the situation that occurs when there is some portion of flat baseline in the space separating the peaks

Baseline resolution

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A lens that, when inserted into the optical train of a microscope, allows the viewer to see an image of the filament; used to establish Koehler illumination. A lens that focuses on the rear aperture of the objective lens assembly

Bertrand lens

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The difference in the refractive indexes of an anisotropic material; can be calculated by subtraction or with a Michel-Levy chart

Birefringence

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Electrophoresis in a capillary tube that exploits electroosmotic flow

Capillary zone electrophoresis/CZE

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A focusing device that utilizes highly polished mirrors in lieu of glass lenses

Cassegrain system

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A component of mass spectrometers in which collision gases are introduced into a high vacuum region to facilitate collisional dissociation of complexes and compounds

Collision cell

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The assembly in a microscope below the sample stage; focuses the beam into a tight cone of light

Condenser/condenser lens

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The space between the lens and the image sensor where the image being filmed will appear in focus to the human eye

Depth of focus

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A material that has two colors due to different absorbances depending on orientation

Dichroic

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An older form of micro-IR in which the diffuse reflections off a sample act as the attenuated IR signal

Diffuse reflection

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Natural spreading of a concentrated band of analyte

Diffusion

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Physical separation of constituent wavelengths by a device such as a prism or grating

Dispersion

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Ionization and fragmentation of molecules entering a mass spectrometer achieved by collision with a stream of electrons produced by a heated filament

Electron impact ionization/quadrupole mass filter

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Transition of an atom or ion from the ground to an excited state via electron promotion among atomic orbitals

Electronic transition

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Flow of ions that occurs in a silica capillary tube exploited in capillary electrophoresis

Electroosmotic flow

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Separation of charged and neutral species based on size-to-charge ratio

Electrophoresis

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An ionization source for LC/MS that applies charge to solvent droplets that evaporate and eventually disperse via Coulombic explosion

Electrospray ionization (ESI)

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In an ATR, a series of reflective adsorptive interactions; multiple internal reflections

Evanescent wave

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A sample preparation technique that removes the analyte from the matrix

Extinction

The lens or lens assembly closest to the sample in optical microscopes

Eyepiece

How large a portion of the sample can be seen in focus at one time

Field of view

A GC detector selective to organic carbon and C-H bonds; based on creation of charged species in the flame

Flame ionization detector (FID)

A cell used to isolate separated analytes in a flowing system long enough to obtain a spectrochemical measurement with an adequate pathlength

Flow cell

The distance along the optic axis of a lens to the principal focus

Focal length

A combination of a separation module with a detector module such as GC-MS (GCMS); hyphen is often omitted

Hyphenated instrument

An extremely hot excitation source for elemental analysis via emission or mass spectrometry. A plasma is not a flame and reaches much higher temperatures, so it can excite a significant portion of the ground state atoms. The plasma is created in the torch portion of the inlet

Inductively coupled plasma (ICP) torch

A plot of the distance traveled in an interferometer by the mirror versus intensity; can also be plotted versus time

Interferogram

Techniques that exploit interference (constructive and destructive) to limit or control the wavelengths of light transmitted from a source to a detector

Interferometry

Gas phase separation of ion/molecule clusters at atmospheric pressure; generically gas phase electrophoresis

Ion mobility spectrometry

In mass spectrometry, a substance that has the same molecular weight or atomic weight of the substance of interest

Isobaric interference

Materials that have the same refractive index regardless of orientation

Isotropic

A method of filtering ions in a collision cell such as an ICP-MS or LC-MSn instruments

Kinetic energy discrimination (KED)

In a microscope, the alignment of lamp and lenses that produces optimal and even illumination

Koehler illumination

A detector that ionizes and fragments molecules and creates a reproducible and usually unique fragmentation pattern that can be used for identification

Mass spectrometer (MS)

The process of a solute moving in and out of stationary phase

Mass transfer

Capillary electrophoresis using micelles and selective partitioning to separate neutral species

Micellar electrokinetic chromatography (MEKC)

Structures formed by surfactants above a critical concentration in water

Micelles

Use of a microscope in conjunction with a spectrometer

Microspectrophotometry

Output of an ion mobility spectrometry

Mobility spectrum

A device such as a prism, filter, or grating that selectively removes all but a narrow range of electromagnetic energy from an impinging source

Monochromator

A sample introduction device used with ICP-MS and other techniques; creates a fine mist for introduction into the instrument

Nebulizer

A GC detector selective to N- and P-containing compounds; similar in design to an FID and includes and alkali salt

Nitrogen-phosphorus detector (NPD)

An ability of a lens to collect light

Numerical aperture (NA)

The lens or lens assembly closest to the sample in optical microscopes

Objective lens

The lens or lens assembly closest to the viewer's eyes in optical microscopes

Ocular lens

Light path that doesn't follow the principle optical axis; set off at an angle

Off-axis

The imaginary line that runs through the point of a curved lens where the curvature is at a maximum; may or may not be the geometric centerline

Optic axis

A compound used to standardize the performance of mass spectrometers to insure intercomparability of spectra

Per-Fluorotributylamine (PFTBA)

A detector that works by detecting photons dispersed in space; one photodiode per geometrical location

Photodiode array (PDA)

A material that has two or more colors due to different absorbances depending on orientation

Pleochroism

Chemical bonds that are altered by passage of light; bonds in which the electron clouds can be distorted by scattering interactions

Polarizable bonds

Light that vibrates in a single plane

Polarized light

A technique that uses polarizing filters in the optical train of a microscope

Polarized light microscopy (PLM)

The point in space where light rays that have passed through a lens will converge

Principal focus

A material such as a synthetic fiber that is ordered but not crystalline in the sense that a solid inorganic material is

Pseudocrystalline

A transition of an excited state to a lower state that occurs without emission of a photon; a transition in which energy is dissipated typically as heat

Radiationless transition

A vibration technique based on scattering and polarizable bonds

Raman spectroscopy

Scattering that results in no change in wavelength; elastic scattering

Rayleigh scattering

A component of mass spectrometers in which collision gases are introduced into a high vacuum region to facilitate collisional dissociation of complexes and compounds

Reaction cell

An image created by a lens that can be projected onto a screen; an image that exists at a plane in space and doesn't require one to look through a lens to see it

Real image

The ability of a lens or optical train to distinguish two objects, = 0.6/NA

Resolving power

An expression of the slowing of light as it propagates along and perpendicular to the optic axis of the material. The greater the difference in speed, the greater the retardation

Retardation

In polarizing light microscopy, the distance (in nm) that separates the emerging perpendicular and parallel rays emerging from a birefringent sample

Retardation distance

An imaging technique that uses interaction of a sample with electrons to create an image

Scanning electron microscope (SEM)

An expression that described the angles of refraction of light when it passes through an interface; (sin(i))/(sin(r)) = n2/n1

Snell's law

"Perfect reflection"; angle of reflection = angle of incidence; occurs at a surface where there is a change in the refractive index

Specular reflection

Scattering interactions that start from the ground state; a type of inelastic scattering

Stokes scattering

A process where energy is absorbed to some degree by a substrate before being reflected

Surface absorption-reflection (SAR)

A series of mass filters placed in tandem (in space or time) such as a triple quadrupole mass spectrometer

Tandem mass spectrometry

A measure of the efficiency and resolving power of a chromatographic column; based on distillation model

Theoretical plates

A device that converts whatever arrives at a detector (photons, ions, etc.) into an electrical signal

Transducer

A plot of HETP versus flow rate; describes three contributing factors to band broadening and thus column efficiency

van Deemter curve

An image created by a lens that doesn't exist in a point in space and one that can't be captured on a screen. It exists only when viewed through the lens

Virtual image

The amount of space available between the stage and the lens of a microscope for sample insertion

Working distance

A technique in which electrons analogous to light where the diffraction pattern relates to crystal structure

X-ray diffraction (XRD)