44
Components of Op,cal Instruments CHEM 314 Skoog n Holler Ch 7

Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

  • Upload
    others

  • View
    12

  • Download
    0

Embed Size (px)

Citation preview

Page 1: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Components  of  Op,cal  Instruments  

CHEM  314  Skoog  n  Holler  Ch  7  

Page 2: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Objec,ves  •  State  the  components  and  phenomena  that  can  be  

probed  with  op,cal  instruments.  •  Recall  the  methods  of  wavelength  isola,on  •  Diagram,  label,  describe,  and  compare  prism-­‐  vs  

diffrac,on-­‐based  monochromators  •  State  and  be  able  to  perform  calcula,ons  related  

to  mono  performance  characteris,cs  and  λ  dispersion.  

•  Recall  UV-­‐Vis  detectors  •  Diagram,  label,  describe,  and  compare  the  

following  detectors:  PMT,  silicon  diode  

 

Page 3: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Op,cal  Instrumenta,on  Phenomena  probed  •  Absorp,on  •  Luminescence  •  Emission    •  ScaQering  

Components  1.  Stable  radia,on  source  2.  Transparent  sample  holder  3.  Wavelength  isola,on  4.  Detector  5.  Signal  processing  

Page 4: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Jablonski  Diagram  

Page 5: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

0.0 0.1 0.2 0.3 0.4 0.50.0

0.2

0.4

0.6

0.8

1.0

Abs

orba

nce

(arb

)

[Kool-aid]

A=1.9 [Kool-aid]r2=0.97

0.0 0.1 0.2 0.3 0.4 0.50.0

0.2

0.4

0.6

0.8

1.0

Abs

orba

nce

(arb

)

[Kool-aid]

Beer’s  Law:  the  rela,onship  between  concentra,on  and  absorbance  

 

A=ε b  [Kool-­‐aid]  b=  path  length  

y=mx  +  b  

ε molar  absorb,vity    

Page 6: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Sources  of  Nonlinearity  of  Beer’s  law    

1.  Solu,on  factors  2.  Non-­‐monochroma,c  light  3.  Not  analyzing  at  lmax    4.  Stray  light  5.  Mismatched  cuveQes  6.  Instrument  noise  

0.0 0.5 1.0 1.5 2.0 2.5 3.00.0

0.5

1.0

1.5

2.0

2.5

3.0

Abs

orba

nce

(arb

)

[Kool-aid]

Page 7: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Components  of  Op,cal  Instruments  

CHEM  314  Skoog  n  Holler  Ch  7  

Page 8: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Building  a  spectroscopic  instrument  

Page 9: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Building  a  spectroscopic  instrument  

This  lecture  will  focus  on  common  components  of  instruments  for  atomic  and  molecular  spectroscopies    

Components  1.  Stable  radia,on  source  2.  Wavelength  isola,on  3.  Transparent  sample  holder/  op,cs  4.  Detector  5.  Signal  processing  

Page 10: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Source  

Why  does  this  chart  differen,ate  between  line  and  con,nuum  sources?  When  would  you  use  a  line  rather  than  con,nuum  source?  

Page 11: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Op,cs  

Page 12: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Sample  cuveQes  

0  

1  

2  

3  

4  

190   490   790   1090  

Absorban

ce    

Wavelength  (nm)  

Quartz  or  plas;c?  

Quartz   Plas,c  

Page 13: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Building  a  spectroscopic  instrument  

Components  1.  Stable  radia,on  source  2.   Wavelength  isola;on  3.  Transparent  sample  holder/  op,cs  4.   Detector  5.  Signal  processing  

Page 14: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Wavelength  selec,on  

Page 15: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Bandwidth  measurements  

Page 16: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Filters  

Page 17: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Filters  

Page 18: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Monochromators  1.  Entrance  slit-­‐  provides  rectangular  op,cal  image  2.  Collima,ng  lens  or  mirror-­‐  makes  light  beams  parallel  3.  Dispersive  element-­‐  disperses  light  into  component  

wavelengths  4.  Focusing  element-­‐  reforms  rectangular  op,cal  image  

focused  on  focal  plane  5.  Exit  slit-­‐  on  focal  plane,  selects  desired  bandwidth  

Page 19: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Monochromators  Prisms  vs  Gra,ngs  

Refrac,on  

Reflec,on  

λ1>λ2  

Consider  the  figures,  is  λ1  or  λ2  the  longer  λ  and  why.    

Page 20: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Monochromators:  Prisms  vs  Gra,ngs  

When  might  a  prism  be  beQer  than  a  diffrac,on  mono?  

Page 21: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Prisms  

Snell’s  law  

Refrac,ve  index  

Page 22: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Prisms   Bunsen  Prism  

Page 23: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Prisms  Cornu  Prism   LiQrow  Prism  

Page 24: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Reflec,on  gra,ng  Monochromator  

λ1>λ2  

hQps://encrypted-­‐tbn0.gsta,c.com/images?q=tbn:ANd9GcS53If5B18udB7pvW7teXaT3q63kQM1QMWVO1Pbt5R-­‐uV1aXeFg0-­‐T4hL0  

Page 25: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

EchelleQe-­‐  diffrac,on  long  edge  

Page 26: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)
Page 27: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Monochromator  Performance  Characteris,cs  1.  Spectral  purity  2.  Dispersion  of  gra,ng  (D)        

 Reciprocal  linear  dispersion  (D-­‐1)  3.  Resolving  power  (R=  λ/Δλ)  4.  Effec,ve  bandwidth  (Δλeff)  5.  Light  gathering  power  (F)      Focal  length  (f)  

Page 28: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Effec,ve  bandwidth  

Page 29: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)
Page 30: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Monochromator  Performance  Characteris,cs  1.  Spectral  purity  2.  Dispersion  of  gra,ng  (D)        

 Reciprocal  linear  dispersion  (D-­‐1)  3.  Resolving  power  (R=  λ/Δλ)  4.  Effec,ve  bandwidth  (Δλeff)  5.  Light  gathering  power  (F)      Focal  length  (f)  

Page 31: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Echelle  Monochromator  

Page 32: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Echelle  Monochromator  

Page 33: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)
Page 34: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Building  a  spectroscopic  instrument  

Components  1.  Stable  radia,on  source  2.   Wavelength  isola;on  3.  Transparent  sample  holder/  op,cs  4.   Detector  5.  Signal  processing  

Page 35: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Detectors  

Page 36: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Detectors  

Lytle,  1974  

Page 37: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Ideal  detectors  1.  High  sensi,vity  2.  High  signal  to  noise  3.  Constant  detector  response  as  a  func,on  of  l  4.  Fast  response  ,me  5.  No  dark  current  6.  Signal  propor,onal  to  radiant  power  7.  Rugged,  cheap,  simple  

 S  =  kP  +  kd  

Page 38: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Photomul,plier  tube  (PMT)  

Page 39: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

pn  junc,ons  

Page 40: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Silicon  photodiode  

Page 41: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Mul,channel  Si-­‐based  detectors  Photodiode  array  (PDA)  Charge  Injec,on  Device  (CID)  Charge  Coupled  Device  (CCD)    

Page 42: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Mul,channel  Si-­‐based  detectors  Photodiode  array  (PDA)  Charge  Injec,on  Device  (CID)  Charge  Coupled  Device  (CCD)    

Page 43: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Mul,channel  Si-­‐based  detectors  Photodiode  array  Charge  Injec,on  Device  (CID)  Charge  Coupled  Device  (CCD)    

Page 44: Components of Optical Instruments - Instrumental Analysis · Op,cal)Instrumentaon ) Phenomenaprobed(• Absorp,on) • Luminescence) • Emission • Scaering) Components 1. Stable)radiaon)source)

Comparing  Detector  Sensi,vity  

detector   λ 1  s   10  s   100  s  PMT   UV   30   6.3   1.8  

Vis   122   26   7.3  PDA   UV   6000   671   112  

Vis   3300   363   62  CCD   UV   31   3.1   0.3  

Vis   17   1.7   0.2  

Harris,  Table  19-­‐2