All Quizzes (no math tho) Flashcards
The description of how a light ray changes direction at a surface between two media with different refractive indicies
snell’s law
The term that applies when two electromagnetic waves have a phase difference of 0 or 360 degrees, or an integral multiple of 360 degrees
coherence
the spatial frequency of an electromagnetic wave that describes the energies involved in atomic and molecular transitions
wavenumber
the ratio of the spectral radiance of a source to that of a black body at the same wavelength and T
effective bandwidth
a device that blocks all radiation with wavelengths greater than a specific wavelength and passes all wavelengths shorter than this wavelength
long wavelength cut off filter
T/F: Normal prism materials show higher refractive indices at shorter wavelengths. This results in shorter wavelengths (i.e. blue light) being more highly refracted than longer wavelengths (i.e. red light)
true
T/F: when an electromagnetic wave travels from a medium of lower refractive index (n1) into a medium of higher refractive index (n2), the wavelength changes and is smaller in n2
false
T/F: Fraunhofer diffraction consists of a central maximum peak with side peaks of gradually decreasing intensity. The central maximum peak is due to light rays that have to travel different distances or different optical path lengths, thus leading to destructive interference
False
T/F: Blazed gratings are characterized by high diffraction orders and large angles of diffraction in order to achieve high resolution
false
T/F: the resolving power of a grating is directly related to the width of the grating and the groove spacing
true
Type of random, fundamental, white noise produced whenever electrons move across a junction or barrier
shot noise
the line shape that results from collisional or pressure broadening
gaussian distribution
a mathematical, liner filter in which the smoothed data are simple linear averaged functions of the input data, and in which the filter window is successively moved along the spectrum point by point
moving average filter
random, nonfundamental, frequency dependent noise that usually manifests itself as a slow drift in the signal
1/f noise
The alteration of some property of a carrier wave by a signal so that the carrier wave encodes the spectral information; moves the signal to a frequency where it is easily distinguished from noise
modulation
Which of the following statements about detectors is true?
a) the sensitivity of a detector is the slope of the curve of detector electrical response vs incident radiant intensity
b) the sensitivity of a detector is equivalent to its detection limit
c) a plot of sensitivity of a detector vs wavelength is called the spectral response of the detector
d) the specific detectivity of a detector is only used when comparing photon detectors in the uv-vis region
a and c
What is the name of a detector consisting of a photosensitive cathode and collection anode separated by intermediate, positively biased dynodes that provides for an electron multiplication cascade of more than 10^6?
photomultiplier tube
What would be the best detector to choose if you wanted to obtain milli-second kinetic measurements of the entire spectrum at once in the UV-VIs region of the spectrum?
silicon photodiode array
Which of the following statements about the advantages of charge-coupled device detectors compared to photomultiplier tubes are true?
a) CCD’s have higher quantum efficiencies than do PMT’s
b) CCD’s respond better to microwave radiation compared to PMT’s
c) CCD’s are integrating detectors and result in higher S/N than do PMT’s
d) CCD’s are multichannel detectors while PMT’s are single element detectors
all of the above
What is the name of a thermal detector based on a surface charge polarization effect that is widely used in FT-IR?
pyroelectric detector
a type of interference in atomic absorption spectroscopy due to particles in the flame that are roughly the same size as the wavelengths of light from the source
light scattering
the background correction technique based on strong magnetic fields that surrounds the sample and splits the atomic energy levels into pi and sigma components
analyte shifted zeeman correction
an alternative to flame atomization method for atomic absorption spectroscopy in which the sample is placed in a sealed tube and dryed/ashed/atomized within seconds to a final T of about 3000K
electrothermal atomizer
a type of interference that results from formation of strong complexes in solution; typically, ions are added that attach to the interfering anions and form stronger complexes than the analyte
low volatility compound formation
the type of atomic spectroscopy method that atomizes a sample by using a high frequency electrical signal produced via a coil that surrounds the sample
inductively coupled plasma
In flame atomic absorption spectroscopy, the purpose of the flame is to produce..
ground state unionized atoms
why is flame atomic emission spectroscopy more sensitive to flame instability than flame atomic absorption methods
small fluctuations in flame temperature create relative large changes in the number of excited state atoms
identify the sequential steps that occur during sample atomization
- nebulization
- desolvation
- vaporization
- atomization
- detection
What are some of the advantages of electrothermal graphite furnace atomic absorption spectroscopy over flame atomic absorption?
high sensitivity with low detection limits - low ppb or better; small sample volumes are feasible without pretreatment
Which of the following statements regarding continuum source background correction in atomic absorption spectroscopy is true?
a) the sample absorbs pi energy levels from the hollow cathode lamp while the background absorbs sigma energy levels from the D2 lamp
b) since atomic lines are very narrow, the emitted radiation from the hollow cathode lamp is absorbed only by the sample, while the blackbody radiation from the D2 lamp is absorbed by the background
c) operating the D2 lamp at high current with short pulse modulation splits the atomic energy levels of the sample
b
T/F: a plasma is an electrically conducting gas containing a large concentration of cations and electrons and a net charge of zero
true
T/F: a hollow cathode lamp is used as the source in a flame atomic emission spectrophotometer
false
T/F: the detection limits of high energy atomic emission methods can be much lower than flame atomic absorption methods, but the precision of AE methods is generally worse than that of AA
true
T/F: an ionization buffer is a more easily ionized species added to a sample that shifts the equilibrium towards the neutral analyte by increasing the concentration of electrons in the flame
true
T/F: multichannel atomic emission instruments are based on echelle monochromators and multichannel detectors for very high resolution
true
the term that describes the ∆v = + 1 change between vibrational energy states v = 0 to v = 1
fundamental vibrational transition
a synchronous motion in which groups of atoms move in phase and with the same frequency
normal mode of vibration
the standing wave electric field intensity that penetrates into the region of lower refractive index under conditions of total internal reflectance
evanescent wave
a potential energy function that exhibits nonparabolic behavior for a diatomic molecular system, and in which V(x) - V(xe) to De as x approaches infinity
morse potential
the term that refers to the physical quantity that must be non zero in order for a vibration to be infrared active
dipole moment
the term that refers to the inherent precision in the wavenumber scale of fourier transform IR spectrometers
conne’s advantage
The encoding of a carrier wave by varying its frequency in accordance with an input signal
modulation
a term that refers to the increased signal to noise ratio that results from the increased signal strength at the detector, and is related to the optical throughput of an interferometric IR spectrometer
Jacquinot’s advantage
The term that describes the situation in a michelson interferometer when the optical path difference of a monochromatic source is equal to δ = λ/2, 3/2λ, 5/2λ,…
destructive interference
the term that refers to the number of measurement subdivisions contained in a spectral range between wavenumber limits ṽmax and ṽmin at resolution ∆ṽ
resolution elements
in fourier transform spectroscopy fellgets advantage refers to
Assume that you have an analog input signal with a maximum spectral frequency of 30 kHz. According to the nyquist therom, what is the sampling rate that must be used to unambiguously digitize this input signal without error?
In order to acquire an attenuated total reflectance infrared spectrum, what conditions must apply?
the IR radiation must approach the interface between two phases from the higher refractive index medium; the angle of incidence of the incoming radiation must be greater than the critical angle
What is an apodization function?
a weighting function that minimizes distortions produced by truncation of the interferogram
The process by which the photon gains energy during an inelastic collision at the expense of the molecule, resulting in scattered photons of higher energy than incident photons
anti-stokes raman scattering
the averaging of a signal over adjacent pixels, or even whole columns, in a multichannel detector to increase signal strength
binning
a common excitation source used in raman that uses neutral atoms with low power consumption. It supports only a single red excitation wavelength
he-ne lasers
the term that refers to an optical device with high absorbance (>10^6) at the laser wavelength, but is designed to allow only stokes shifted wavelengths to pass
edge filter
the separation of electrons and protons in a molecule that results from the intense electric and magnetic fields produced by the electromagnetic radiation of a laser
induced dipole moment
the term that refers to the case in which an excited state electron reverses its spin, in which the molecules total spin angular momentum quantum number is S = 1
T1 or triplet state
decrease of fluorescence intensity that occurs due to the dynamic solution diffusion of the excited state fluorophore and its interaction with another molecule, thereby decreasing its excited state lifetime
collisional quenching
the radiative process of photon emission that occurs primarily from the v’ = 1 level with S1 with a time scale of 10^-9 seconds
fluorescence
a non-radiative means of dissipating excess vibrational energy in an excited electronic state, usually through collision with solvent molecules
vibrational relaxation
the term that refers to the fact that the internuclear distance in a vibrating molecule may be regarded as fixed during an electronic transition
frank condon principle
What expression describes the process that occurs during fluorescence emission?
S1 to S0
the formation of excimers is an example of
the intermolecular interaction of an excited state molecule and the ground state of a second, identical molecule
which of the following is a common excitation source used in raman spectroscopy:
a) an Ar hollow cathode lamp
b) an Ar+ ion laser that emits radiation at 514.5 nm
c) a SiC globar
d) a pulsed CO2 laser operating at 10.6 micrometers
b
the following expression refers to what spectroscopic process? v’’ = 0 to v’ = 3
an electronic transition that begins in the ground vibrational level in an excited electronic state
major advantages of raman scattering when compared with IR
water is a strong IR absorber, but a weak raman scatterer, therefore aqueous solutions can be more easily studied with raman; low cost optical fibers may be used in the visible and near infrared spectral regions to transmit the raman scattered radiation for remote sampling
the largest abundance peak or the one with the highest response in the mass spectrum
base peak
the method that uses a pulsed ionization source to generate and accelerate ions to a constant kinetic energy; ions are sorted temporally
time of flight analyzer
a desorption technique in which the condensed phase sample is bombarded with energetic Ar0 atoms
fast atom bombardment
the gas phase acid base ionization reaction mechanism that results in a (m-1)+ peak
chemical ionization or hydride transfer
the MS method that takes into account both the directional and kinetic energy distribution of the ion to increase resolution
double focusing analyzer
method to analyze relatively small, volatile analytes. sample introduced by GC or liquid/solid probe. Mass ranges to 1000 Da. Gas phase, hard method, provides structural information
electron ionization
method to analyze relatively small, volatile samples introduced with GC or liquid/solid probe with a mass range to 1000 Da. Gas phase, soft method, proton transfer common
chemical ionization
Method to analyze peptides, proteins, nucleotides, non-volatile samples. easily coupled to chromatography. Mass to 200,000 Da. soft method, multiply charged ions, high electric field.
electrospray ionization
method to analyze carbohydrates, organometallics, peptides, and non-volatile compounds. sample mixed in viscous matrix. mass to 10,000 Da. desorption, soft method, energetic atomic beam.
fast atom bombardment
Method to analyze peptides, proteins, nucleotides. Sample mixed in solid matrix. Mass to 500,000 Da. Desorption, soft method, molecular ion peak predominates
matrix assisted laser desorption
