Exam 2

Question 1

Tungsten Halogen Lamp

Answer 1

• 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)

Question 2

Jablonski Diagram

External Conversion

Answer 2

Question 3

Jablonski Diagram

Flourescence

Answer 3

Question 4

Absorbance

Answer 4

• 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

Question 5

Define Quantized Vibrational States

Answer 5

• arising from the frequency of inter atomic (bond) vibrations

Question 6

Purpose of Wavelength Selector

Answer 6

• 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

Question 7

Name That Acronym

F.A.A.S.

Answer 7

Flame Atomic Absorption Spectroscopy

Question 8

Describe Energy States in Chemical Species

Answer 8

• 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

Question 9

What is Photoelectric Effect

Answer 9

• 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

Question 10

What is the basic schematic of intrumentation?

Answer 10

Source—>Sample—>Wavelength Selctor—> Detector

Question 11

Jablonski Diagram

Internal Conversion

Answer 11

Question 12

Jablonski Diagram

Absorption

Answer 12

Question 13

Question

If the excitation wavelength is 520nm, what is the Change in excited Energy?

Answer 13

E = hc/wavelength

h = 6.63E-34 Js

answer is 3.83E-17 J

Question 14

Define Quantized Electronic States

Answer 14

• arising from path of electrons around nucleus

Question 15

L.A.S.E.R.

Answer 15

• 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

Question 16

Define Black Body Radiation

Answer 16

• 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

Question 17

Name a source that is a combination of continuum/line.

Answer 17

1. Deuterium Lamp
2. Xenon Arc Lamp

Question 18

What parts are needed for the following instrument?

ICP-OES

Answer 18

• source
  
  • plasma
• sample holder
  
  • plasma
• wavelength slector
  
  • diffraction grating coupled with prism
• detector
  
  • segmented CCD

Question 19

What parts are needed for the following instrument?

UV-Vis

Answer 19

• source
  
  • tungsten halogen lamp or deuterium lamp
• sample holder
  
  • cuvette
• wavelength selector
  
  • diffraction grating
• detector
  
  • PMT or PDA

Question 20

Name That Acronym

L.A.S.E.R.

Answer 20

Light Amplification by Stimulated Emission of Radiation

Question 21

What is a Jablonski Diagram

Answer 21

• shows where energy is going and what is the sample doing with the energy
• describe the energy between energy levels and distances

Question 22

The ______ the conjugation, the _____ the emission is

Answer 22

• 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

Question 23

Name That Acronym

P.D.A

Answer 23

Photo Diode Array

Question 24

Types of Grating

Answer 24

• Echellete-type
  
  • what we discussed about
• concave type
• holographic type

Question 25

Jablonski Diagram Scattering

Answer 25

Question 26

Define Line Sources

Answer 26

* one of the three types of sources * emits very specific wavelengths

Question 27

Prism

Answer 27

* 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

Question 28

Types of Wavelength Selectors

Answer 28

* seperated in space * filters * absorbance filters * beam splitters * prisms * gratings * seperated in time * Michelson Interfometer

Question 29

What is a typical unit for absoption and emission spectroscopy?

Answer 29

* Counts per Second (cps) * measure of intensity, literally how many photons are striking the detector per second, used for emission and scattering spectroscopy

Question 30

Name That Acronym C.M.O.S.

Answer 30

Complimentary Metal Oxide Semi Conductor

Question 31

Jablonski Diagram Electron EM Emission

Answer 31

Question 32

Hollow Cathode Lamp

Answer 32

* 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

Question 33

Note for Bond in Spectrums

Answer 33

* for ultraviolet/visble absorption, molecular spectra almost always appear as bands, rather than discrete peaks

Question 34

Jablonski Diagram Thermal Energy

Answer 34

Question 35

Name That Acronym C.P.S.

Answer 35

Counts Per Second

Question 36

What parts are needed for the following instrument? FAAS

Answer 36

* source * hallow cathode lamp (HCL) * sample holder * flame * wavelength selector * diffraction grating * detector * PMT

Question 37

Define Spectroscopy

Answer 37

* study of the interaction of light with matter * measure the physical response of a sample to a light stimulus

Question 38

Jablonski Diagram Intersystem Crossing

Answer 38

Question 39

Xenon Arc Lamp

Answer 39

* huge potentials between electrodes cause Ionization * operate at 6,000K most closely imitate sunlight

Question 40

Transmittance (T or %T)

Answer 40

* description of radiant power passing through sample undisturbed T = P/P₀

Question 41

Name That Acronym C.C.D

Answer 41

Charged Coupled Device

Question 42

Jablonski Diagram Thermal/Electrical Excitation

Answer 42

Question 43

Define Continuum Source

Answer 43

* one of the three types of sources * emit many wavelengths simultaneously

Question 44

Name That Acronym I.C.P. - O.E.S.

Answer 44

Inductively Coupled Plasma Optical Emission Spectroscopy

Question 45

Jablonski Diagram Single Excited State

Answer 45

- when an electron moves from one energy level to another without flipping

Question 46

Grating

Answer 46

* transmission type * reflection type * widely used in modern instruments

Question 47

Define Line/Continuum Sources

Answer 47

* one of the three types of sources * a combination of line source and continuum source

Question 48

Jablonski Diagram Phosphorescence

Answer 48

Question 49

Jablonski Diagram Triplet Excited State

Answer 49

- when the electron flips its spin from up to down or vice versa

Question 50

Name That Acronym P.M.T.

Answer 50

Photomultiplier Tube