CO-ORDINATION COMPOUNDSOPTICAL PROPERTIES

By Nikhat.S.H.MSc-II,Paper-1S.I.E.S

Topics-

Luminescence

F-Centres

Birefringence

Anti-stokes Phosphors

Lasers-

1. Ruby laser

2. Neomydimium laser

Luminescence

Phosphors

Activators

Sentitizers

F-Center

F-center, Farbe center or color center

A type of crystallographic defect

F-centers are often paramagnetic and can then be studied

Number of F-centers α colour intensity of the compound.

•Producing F-centres

e.g., NaCl heated in a metallic Na atmosphere.

Na0 → Na+ + e−

Na+ is incorporated at NaCl crystal.Cl− vacancies are generated, because of the excess of Na+.

•These vacancies capture available electrons, e-

. Ionizing radiation can also produce F-centers.

Birefringence

Danish scientist Rasmus Bartholin in 1669

Displacement of light rays with perpendicular polarization through a birefringent material.

Birefringence

Crystals with asymmetric crystal structures are often birefringent, as well as plastics under mechanical stress.

double refraction

Doubly refracted image as seen through a calcite crystal

A calcite crystal laid upon a graph paper with blue lines showing the double refraction

Applications

Liquid crystal displays

light modulators

Medicine-medical diagnostics

Anti-Stokes Phosphor

Stokes shift

Anti-Stokes shift

Yttrium oxysulfide doped with gadolinium oxysulfide

Lasers Light Amplification by Stimulated Emission of

Radiation

Population Inversion-More active centres in excited state than in ground state

Ruby laser

Ruby -gain medium

Theodore H. "Ted" Maiman at Hughes Research Laboratories on May 16, 1960.

Energy levels of Cr3+ in ruby laser

Applications

High - brightness holographic camera systems with long coherent length.

High - power systems useful for frequency doubling into the UV spectrum.

Drilling holes in hard materials,e.g.diamond

Cosmetic dermatology and tattoo removal

Neodymium Lasers

1964 at Bell Labs

The crystal host used -Y3A15012 (yttrium

aluminium gamet, or YAG), Nd:YAG.

The laser transition - 1064 nm, which is in the near infrared region.

Energy Levels of Nd3+

Applications

Medicine-

Opthalmology

Oncology

Dentistry

manufacturing for engraving, etching, or marking a variety of metals and plastics

cutting and welding steel

laser hair removal

References

C.N.R. Rao and J.Gopalkrishnan New Directons in Solid State Chemistry, 2nd Ed., Combridge University Press. 1997

Ulrich Muller, Inorganic structural Chemistry, 2nd edition, John Wiley and Sons, Chichester, 1993.

Gary L.Miessler and Donald A.Tarr, Inorganic Chemistry, 3rd edition , Pearson Education, Inc., 2004.

Thank You