1.  SPECTROSCOPY 101 Arkansas 2-Day October 2013 Lisa McGaw OSU lmcgaw@me.com

2. Spectroscopy  Spectroscopy –(In plain English) - a technique used to help us understand the molecular structure of matter by observing motion in response to the absorption of energy

3. TYPES OF SPECTROSCOPY  IR  UV-VIS  MASS SPEC  PES  Many others – microwave, esr; x-ray; NMR; Raman; atomic absorption, etc.

4. Electromagnetic Radiation and Transitions E = hν and c = λν RadioMicrowaveFar IRIRVisibleUVX-ray 10 m1 x 10 -2 to 5 x 10 -4 m 5 x 10 -4 - 1.5 x 10 -5 m 1.5 x 10 -5 - 7 x 10 -7 m 7 x 10 -7 to 4 x 10 -7 m 4 x 10 -7 to 1 x 10 -7 m 1 x 10 -7 to 1 x 10 -16 m Nuclei (nmr) Electron spin (esr) Molecular vibrations (IR) Valence electrons (UV-Vis) (Mass spec) Inner electrons (PES) (Mass spec)

5. IR Spectroscopy  1.D (LO 1.15)  Transitions in molecular motion – rotational, vibrational and electronic (low energy to high energy)  https://en.wikipedia.org/wiki/Infrared_spectroscopy https://en.wikipedia.org/wiki/Infrared_spectroscopy  Detect presence of different types of bonds  Useful for identification and structural analysis of organic and inorganic compounds.

6. Dichloromethane near IR

7. UV- Vis Spectroscopy  1.D (LO 1.15 and LO 1.16) (SP 4.1, 4.2, 5.1 and 6.2)  Transitions in electronic energy levels  Used to probe electronic structure  Molecules absorb UV or Visible light  A = abc (absorption directly related to concentration)

8. How Do the Colors Relate?  UV region – not visible to our eyes  Visible region – ROYGBIV  Low energy  higher energy Color AbsorbedRed – OrangeYellow-GreenBlue-Violet Color Transmitted Blue, GreenPurpleRed, orange, yellow

9. UV Spectroscopy

10. Blue Dye

11. Standard Curve

12. Mass Spectroscopy  1.D (LO 1.14) (SP 1.4 and SP 1.5)  Demonstrates direct evidence of different isotopes from the same element  Average atomic mass estimated from mass spec data  Solid, liquid or gas sample is ionized;  Ions are separated according to mass to charge ratio

13. Isotopic Data for Bromine (web elements.com)

14. PES Spectroscopy  1.B (LO 1.7* also LO 1.5, 1.6, 1.8) (SP 1.5, 5.1, 6.2)  Photoelectric effect – incident light ejects electrons  Energies provide evidence for shell model  Intensity of signal implies number of electrons at that energy level

15. PES Spectroscopy