Polarization Modulation with PEM for CD (courtesy Hinds Instr.)

Linear Dichroism Schematic (courtesy Hinds Instr.) Spectrometer UV or IR Linear polarizer PEM

(courtesy Hinds Instruments) Linear Dichroism - Reflection (IRRAS) (courtesy Hinds Instruments) Variable angle of incidence Surface can be metal (high reflection, often grazing incidence) or dielectric, or even air-water interface For film on liquid use Langmuir-trough for sample--studies of peptides and proteins in membranes possible, orientation from polarization

ATR Polarization Measurements IR beam multiply reflects inside crystal -- penetrates surface keeps polarizations: Eperp in surface, Epara partially out In from FTIR E Crystal- Typ: Ge, ZnSe High index for refl. out Sample coated on crystal

Schematic – External reflectance FTIR & L-B trough Dluhy, App.Spec.Rev.2000

Light—Electro-Magnetic (E-M) radiation Tool for probing quantum mechanical states l E || z B || x B | E n = c/l x z y k || y