1 / 12

Describing a Real Source

Describing a Real Source. 1) Identify l m of real source and adjust T in to line up l m 2) The ratio of: 3) Measure T w ( l ) to calculate e ( l ). Ingle and Crouch, Spectrochemical Analysis. Nernst Glower. Rare earth oxides formed into a cylinder (1-2 mm diameter, ~20mm long)

merlin
Download Presentation

Describing a Real Source

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Describing a Real Source • 1) Identify lm of real source and adjust T in to line up lm • 2) The ratio of: • 3) Measure Tw(l) to calculate e(l) Ingle and Crouch, Spectrochemical Analysis

  2. Nernst Glower Rare earth oxides formed into a cylinder (1-2 mm diameter, ~20mm long) Pass current to give: T = 1200 – 2200 K Can operate in air (no need for glass/quartz enclosure) Ingle and Crouch, Spectrochemical Analysis Douglas A. Skoog and James J. Leary, Principles of Instrumental Analysis, Saunders College Publishing, Fort Worth, 1992.

  3. Globar Silicon Carbide Rod (5mm diameter, 50 mm long) Heated electrically to 1300 – 1500 K Positive temperature coefficient of resistance Electrical contact must be water cooled to prevent arcing Ingle and Crouch, Spectrochemical Analysis

  4. Tungsten Filament Heated to 2870 K in vacuum or inert gas Useful Range: 350 – 2500nm Ingle and Crouch, Spectrochemical Analysis

  5. Tungsten / Halogen Lamp I2 or Br2 added Reacts with gaseous W near the quartz wall to form WI2 W is redeposited on the filament Gives longer lifetimes Allows higher temperatures (~3500 K) and thus higher apparent brightness

  6. Arc Lamps Electrical discharge is sustained through a gas or metal vapor Continuous emission due to rotational/vibrational energy levels and pressure broadening Ingle and Crouch, Spectrochemical Analysis

  7. H2 or D2 Arc Lamps D2 + Ee- D2*  D’ + D” + hn Energetics: Ee- = ED2* = ED’ + ED” + hn Useful Range: 185 – 400 nm Ingle and Crouch, Spectrochemical Analysis

  8. Hg Arc Lamp Continuum + line source High power source Often used in photoluminescence Ingle and Crouch, Spectrochemical Analysis

  9. Hollow Cathode Discharge Tube Apply ~300 V across electrodes Ar+ or Ne+ travel toward the cathode If potential is high enough cations will sputter metal off the electrode Metal emits photons at characteristic atomic lines as the metal returns to the ground state Douglas A. Skoog and James J. Leary, Principles of Instrumental Analysis, Saunders College Publishing, Fort Worth, 1992.

  10. Hollow Cathode Discharge Tube Line widths are typically 0.01 – 0.02 Å FWHM Ingle and Crouch, Spectrochemical Analysis

  11. Light-Emitting Diodes Operate with 30-60 mW of power - ~80% efficiency Long lifetimes, stable output www.wikipedia.org

  12. Are you getting the concept? List one light source with each of the following characteristics.

More Related