chemical spectroscopy Flashcards
deals with the interaction of light with chemical substances
chemical spectroscopy
only one part of the electromagnetic spectrum made of electromagnetic wave
light/visible light
parts pf light
- electric field component
2, magnetic field component
a disturbance that transmit energy
wave
speed of light
3.0 × 10⁵ m/s
speed of light =
wavelength × frequency
wave energy =
planck’s constant × frequency
electromagnetic spectrum (from lowest to highest)
- radio waves
- microwaves
- infrared
- visible light
- ultraviolet
- X-rays
- Gamma rays
type of quantum change in IR
change in configuration: bending, stretching, and scissoring
type of quantum change in UV-VIS
change in electron configuration: molecular and atomic
spectroscopic measurements
emission and absorption
sample is exited by applying heat or electricity
emission
when electrons return to ground state, they emit radiation characteristics of a given atom
emission
measures the light absorbed as a function of wavelength
absorption
components of various types of optical spectroscopy
- source
- wavelength selector
- sample container
- radiation detector
- signal processing and read out unit
isolates the desired wavelength band so that the only the band of interest is detected and measured
monochromator
types of monochromator
- grating
- prism
monochromator with 100-40,000 nm range
grating monochromator
monochromator with 120-30,000 nm range
prism monochromator
detector
phototubes
works via photoelectric effect
phototubes
UV-Vis spectrometer
source > monochromator >< shutter >< sample (blank) > detector> signal processor
instrument components
- source
- monochromator (entrance slit, dispersion device, and exit slit)
- sample
- detector
two ways of expressing amount of light
- transmittance
- absorbance
human eye serves as the detector
colorimeter
use a absorption or interference filters for wavelength selection and a photoelectric device for measuring radiant power
photometer
uses a monochromator or a polychromator in conjunction with a transducer to convert the radiant intensities into electrical signals
spectrometers
special type of spectrometer in which wavelength can be varied continuously, thus making scanning of absorption spectra possible
spectrophotometers
one of the most useful techniques in investigating the structure of organic compounds
Infrared spectroscopy
used as a tool for qualitative and quantitative determination of molecular species
infrared spectroscopy
energy of IR photon insufficient to cause electronic excitation but can cause vibrational or rotational excitation
infrared absorption
