Exam 2 Flashcards
Tungsten Halogen Lamp
- type of continuum source
- house hold product is called incandescent bulb
- intrument bulb
- evacuated quartz is partially backfilled with I2 gass
- as W sublimes, reactive WI2 is created, redeposits W on filament
- lasts longer at a higher temperature (3,500K)
Jablonski Diagram
External Conversion
Jablonski Diagram
Flourescence
Absorbance
- description of radiant power that interacts with energy states of a sample
A = -log10(P/P0)
A = €bc
- describes energy that goes through a sample undisterbed
- reveals the opposite of what transmitance reveals
- allows for linear relationship between concentration and light interaction
Define Quantized Vibrational States
- arising from the frequency of inter atomic (bond) vibrations
Purpose of Wavelength Selector
- to either allow a single frequency to interact with sample or to reach transducer for recording
- no wavelength selector is able to choose a single frequency
- provides a band of radiation
Name That Acronym
F.A.A.S.
Flame Atomic Absorption Spectroscopy
Describe Energy States in Chemical Species
- atoms, molecules and ions exist in discrete energy states
- absorption or emission of light will only occur when the energy of light is equal to the energy difference of two states of the absorbing/emitting species
What is Photoelectric Effect
- the emission of electrons or other free carriers when light is shone onto a material
- Electrons emitted in this manner can be called photo electrons
- light of single frequency strikes cathode, if anode is positive to cathode, constant current
- as anode becomes negative, current decreases
- @ some negative potential, current stops
- stopping voltage depends on
- photocathode material
- frequency of light
- stopping voltage does not depend on intensity of light
What is the basic schematic of intrumentation?
Source—>Sample—>Wavelength Selctor—> Detector
Jablonski Diagram
Internal Conversion
Jablonski Diagram
Absorption
Question
If the excitation wavelength is 520nm, what is the Change in excited Energy?
E = hc/wavelength
h = 6.63E-34 Js
answer is 3.83E-17 J
Define Quantized Electronic States
- arising from path of electrons around nucleus
L.A.S.E.R.
- a type of line source
- Light Amplification by Stimulated Emission of Radiation
- unique since it produces extremely narrow emissionlocalized to a small spot coherent for many meters
Define Black Body Radiation
- intensity and peak emission wavelength are a function of Temperature
- as T increases, the total intensity increases and there is a shift to higher energies
- toward visible & UV
- heat induces broad band emission
- more heat = smaller wavelength = more light to the point it appears white
- the reason why “white” hot is hotter than “red” hot
Name a source that is a combination of continuum/line.
- Deuterium Lamp
- Xenon Arc Lamp
What parts are needed for the following instrument?
ICP-OES
- source
- plasma
- sample holder
- plasma
- wavelength slector
- diffraction grating coupled with prism
- detector
- segmented CCD
What parts are needed for the following instrument?
UV-Vis
- source
- tungsten halogen lamp or deuterium lamp
- sample holder
- cuvette
- wavelength selector
- diffraction grating
- detector
- PMT or PDA
Name That Acronym
L.A.S.E.R.
Light Amplification by Stimulated Emission of Radiation
What is a Jablonski Diagram
- shows where energy is going and what is the sample doing with the energy
- describe the energy between energy levels and distances
The ______ the conjugation, the _____ the emission is
- higher; longer
- one of the rasons why benzene rings are so stable
- benzene is flate molecule
- the more conjugation a molecule a molecule is, the more it will appear in the visible spectrum
Name That Acronym
P.D.A
Photo Diode Array
Types of Grating
- Echellete-type
- what we discussed about
- concave type
- holographic type
Jablonski Diagram
Scattering
Define Line Sources
- one of the three types of sources
- emits very specific wavelengths
Prism
- dispersion allows for a wavelength depenent refraction angle
- seperates white light into the color light
- shorter wavelength are more spaced out than longer wavelength
- when shinning white light through a prisim, we would probably see more blue/violet color than red
Types of Wavelength Selectors
- seperated in space
- filters
- absorbance filters
- beam splitters
- prisms
- gratings
- filters
- seperated in time
- Michelson Interfometer
What is a typical unit for absoption and emission spectroscopy?
- Counts per Second (cps)
- measure of intensity, literally how many photons are striking the detector per second, used for emission and scattering spectroscopy
Name That Acronym
C.M.O.S.
Complimentary Metal Oxide Semi Conductor
Jablonski Diagram
Electron EM Emission
Hollow Cathode Lamp
- type of line source
- cathode is made froma metal that emits at the desired wavelength
- design of lamp ensures that emission is in center of lamp and highest probability that metal will reabsorb to cathode surface
Note for Bond in Spectrums
- for ultraviolet/visble absorption, molecular spectra almost always appear as bands, rather than discrete peaks
Jablonski Diagram
Thermal Energy
Name That Acronym
C.P.S.
Counts Per Second
What parts are needed for the following instrument?
FAAS
- source
- hallow cathode lamp (HCL)
- sample holder
- flame
- wavelength selector
- diffraction grating
- detector
- PMT
Define Spectroscopy
- study of the interaction of light with matter
- measure the physical response of a sample to a light stimulus
Jablonski Diagram
Intersystem Crossing
Xenon Arc Lamp
- huge potentials between electrodes cause Ionization
- operate at 6,000K most closely imitate sunlight
Transmittance (T or %T)
- description of radiant power passing through sample undisturbed
T = P/P0
Name That Acronym
C.C.D
Charged Coupled Device
Jablonski Diagram
Thermal/Electrical Excitation
Define Continuum Source
- one of the three types of sources
- emit many wavelengths simultaneously
Name That Acronym
I.C.P. - O.E.S.
Inductively Coupled Plasma
Optical Emission Spectroscopy
Jablonski Diagram
Single Excited State
- when an electron moves from one energy level to another without flipping
Grating
- transmission type
- reflection type
- widely used in modern instruments
Define Line/Continuum Sources
- one of the three types of sources
- a combination of line source and continuum source
Jablonski Diagram
Phosphorescence
Jablonski Diagram
Triplet Excited State
- when the electron flips its spin from up to down or vice versa
Name That Acronym
P.M.T.
Photomultiplier Tube
