Optical Spectroscopy with dispersive Spectrometers
Basics - Building Blocks - Systems - Applications

This page summarizes chapter 3 of the book
"Applications of Dispersive Optical Spectroscopy Systems",
ISBN 9781628413724, SPIE monographs, Bellingham, WA, USA

Application E2-
Emission Spectroscopy

This page presents the directory, the signs and symbols, conversions, and equations of the book, while the details are an exclusive part of  the book.

E2.0 Introduction
Naturally, every measurement at a radiating object, is an emission measurement. But, it is common sense to use the name "Emission Spectroscopy" especially for applications, targeting excited molecules, plasmass, or atoms. Often, the spectrum undergoes changes over time, or follows a pulsed excitation. Both require synchronization and/or time resolution. We will shed light on the emission application of:
AES - Atomic Emission Spectroscopy - E2.1
CL   -  Cathodo Luminescence - E2.2
ICP -   Spectroscopy at inductively coupled plasmas - E2.3
F-OES  - Spark Emissions Spectroscopy - E2.4
LA -     Laser Ablation - E2.5
LIBS - Laser induced Breakdown Spectroscopy - E2.5
LIP -    Spectroscopy at Laser induced plasmas - E2.5
LD -     Laser induced Plasma Deposition - E2.5
PE -     Plasma Etch Spectroscopy - E2.6
The measurement of Laser spectra, combustion spectra, and of solar and stellar light per definition does not belong to the Emission group. But, as the measurement technique from the instrumental view is similar, they are added:
LS  -     Laser Spectroscopy - E2.7
SolEm and StelEm - solar and stellar Emission - E2.8
CombEm
- Emission Spectroscopy of Flames and Explosions - E2.9.

E2.0.1 Instrumental Technology for the Acquistion of Emission Spectra
E2.0.2 Typical Emission Spectra
Either plasmas, as well as atoms in the excited state, emit locally exactly defined spectral lines, having bandwidths clearly below 1 nm. The more different molecules make up the sample, the more lines are to be expected.

Grafik E2.1die Emissionslinien von 55 Molekülen

Graph E2-1 shows the Plasma Emission Spectra of 55 different Molecules, used in Semiconductor Technology.
Grafik E2.2 Linienspektrum gedehnt

Graph E2-2 demonstrates the same Plasma Emission Lines as above, reduced to an Interval of 50 nm.
E2.0.3 Set-up based on the 2-D Echelle Spectrometer
E2.0.3.1 Stationary 2-D Echelle Spectrometer
In chapter 3-"Configuration", the function of the 2-D Echelle is described under 3.5.3. In table "2-D Echelle Parameters", a system for the fast, parallel detection between 195 and 950 nm is presented. That table is repeated here:

Wavelength

Grating Order

Interval per Order

Vertical Position at CCD

Pixel-Reserve/ Order

Orientation versus Horizon

Bandwith per Pixel

nm

 

nm

mm

 

degree

pm

1000

52

18.4

-12.4

 

 

 

950

55

17.7

-12.15

6

-0.5

8.6426

900

58

16.5

-11.93

6

-0.6

8.0566

850

61

15.7

-11.7

5

-0.6

7.6660

800

65

14.7

-11.5

3

-0.6

7.1777

750

70

13.8

-11.33

3

-0.7

6.7383

700

74

12.9

-11.13

3

-0.7

6.2988

650

80

12.0

-10.9

4

-0.8

5.8594

600

87

11.0

-10.52

4

-0.9

5.3711

550

95

10.1

-10.17

4

-0.9

4.9316

500

104

9.2

-9.6

5

-1.0

4.4922

460

113

8.5

-9.1

4

-1.2

4.1504

420

124

7.7

-8.52

6

-1.3

3.7598

380

137

7.0

-7.3

7

-1.5

3.4180

340

153

6.3

-5.85

7

-1.8

3.0762

315

166

5.8

-4.5

7

-2.0

2.8320

290

180

5.3

-3.25

8

-2.3

2.5879

265

197

4.9

-1.18

10

-2.9

2.3926

240

217

4.4

1.7

13

-3.4

2.1484

215

243

4.0

6.7

17

-4.4

1.9531

195

267

3.6

12.81

21

-5.9

1.7578

E2.0.3.2: 2-D Echelle Spectrometer with small Detector Surface
E2.0.3.3 MCP-2-D-Echelle Spectrometer
E2.0.4 Scanning (Echelle) Spectrometers
E2.1 AES - Atomic Emission Spectroscopy

Graph E6-E2-3 Basic principle of an AES

Graph E2-3 features the principle of an Atomic Emission Spectrometer.
Graph E2-4 the Rowland Spectrograph

Graph E2-4: Emissions Spectrograph with Rowland Configuration.
Thermal Background:
E2.2 CL - Cathodo Luminescence Spectroscopy
If a ray of electrons hits solid material, it will pump excessive energy into the molecular/atomic structure. Hence, they will be put to excited states, and will emit specific line spectra at relaxation. The process is called cathodo luminescence - CL. In needs to happen in vacuum to allow the electron beam to travel to the sample. A typical every-day application is the cathode ray tube of TV systems.
Graph E2-5  Cathodo Luminescence System
Graph E2-5 displays the principle of a Cathodo Luminescence Spectrometer
.

E2.3 ICP - Spectroscopy at inductively couples Plasmas

Graph E2-6 Principle of the ICP-OES
Graph E2-6: the ICP Spectrometer.

Thermal Background
:

2.3.1 ICP Examples:
The element Uranium provides several hundred spectral emission lines, creating an echellogram like that:
Echellogram of Uranium
Graph E2-6.1: 2-D Echellogram of Uranium.
Echellogram of Ytterbium
Graph E2-6.2: 2-D Echellogram of Ytterbium.

E2.4 F-OES - Spark Emission Spectroscopy
The spark emission spectrometer is a frequently used method in metallurgy. It is used to define the material mix in metallic alloys. The sample must be an electrically conductive one. Similar to ICP, the method can be applied in the open atmosphere or in a chamber with inert gas. The sample is fixed to the table, which also represents the cathode. After that, the tip of the spark gap, which is the anode, is adjusted closely above the point of analysis. The high voltage supply generates a short spark, which atomizes sample material out of the surface. The measurement either works as described before, by a monochromator, or a Rowland spectrograph, or a 2-D Echelle spectrograph.
Graph E2-7 the spark emission spectrometer
Graph E2-7: the Spark Emission Spectrometer.

E2.5 Laser Ablation (LA), also called Laser induced Breakdown Spectroscopy (LIBS), or Laser induced Plasma Spectroscopy (LIP), and Laser Deposition (LD)

Graph E2-8 Laser Ablation
Graph E2-8: the Laser Ablation System.

E2.6 PE - Plasma Etching

Graph E2-9 Plasma Etch System
Graph E2-9, Principle of the Plasma Etch Equipment.


Graph E2-10, Simulation of a Plasma Etch Process.

A typical endpoint detector

E2.7 LS - Laser Emission Spectroscopy
E2.8 SolEm
and StelEm - solar and stellar Emission
E2.9 CombEm - Emission Measurements at Explosions and Flames (Combustions)
are always critical in time. In the case of an explosion, one wants to know, what kind of spectrum appears at what geometrical point, and at what time during the blast. Dealing with flames, the researcher wants to know for instance, how uniform it is, or what are the turbulences, how the temperature is distributed, and more parameters. So, the difference in both applications is time. Explosions always require short exposures for imaging and spectroscopy. A spectroscopy system may look like this:
Graph E2-11 a time resolved combustion system
Graph E2-11 Principle of a Spectroscopy System to Measure Explosions.

As combustions expose high temperatures, Planck´s algorithms for the calculation of temperatures, are applied for the place and time detected.
Grafik E2-12 thermal background
Graph E2-12 The Impact of Temperature to the Spectrum measured.
Planck´s radiation rules apply to all kind of combustions,

External Source Indication:
The echellograms in graphs E2-6.1, and E2-6.2, showing the spectra of Uranium and Ytterbium, are courtesy of Thermo Fisher Scientific GmbH, D-63303 Dreieich, Germany.

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Status of March 2012