L10: Spectroscopy Flashcards
What is the definition of spectroscopy?
The use of electromagnetic radiation to characterize matter
How do molecular scientists use spectroscopy in their work?
To identify and characterize molecules, atoms and sub-atomic particles
What is the relationship between energy, Planck’s constant, and frequency in spectroscopy?
Energy is directly proportional to frequency
What is the equation for energy of light?
E = hv
h= planck’s constant
v= frequency of electromagnetic radiation
List these from shortest wavelength to longest wavelength
- ultraviolet
- x-ray
- visible
- microwave
- gamma ray
- infrared
- radio
Radio
Microwave
Infrared
Visible
UV
X-ray
Gamme ray
2 types of wave interference
1) constructive interference
2) destructive interference
Describe constructive interference
2 separate waves of same frequency results in a larger amplified wave
Describe destructive interference
2 different waves cancel each other out
e.g noise cancelling waves
What role does resonance play in spectroscopy?
Causing energy absorption at a specific frequency
How does absorbance & transmission spectroscopy work?
When light passes through a substance, some wavelengthsare absorbed and some are transmitted
- light we see is light that is NOT ABSORBED
What does the Beer-Lambert law describe in absorbance spectroscopy?
Relationship between absorbance, path length, and concentration
What does Beer-Lambert Law (UV-Vis spectroscopy) used for?
To quantify light absorption by a sample
What type of spectroscopy uses longer wavelengths and lower frequencies than UV-Vis spectroscopy?
Infrared Spectroscopy
What does infrared spectroscopy measure?
Vibrational transitions in molecules: stretching, bending & twisting
How does infrared (IR) spectroscopy work?
Uses longer wavelengths than UV-vis
What is fluorescence spectroscopy particularly good at detecting compared to other types of spectroscopy?
Single molecule detection and analyses
Applications of fluorescence spectroscopy
1) single molecule detection
2) fluorescence microscopy
3) FRET (fluorescence energy transfer): “molecule ruler”
What are fluorophores?
Molecules that exhibit fluorescence
Why is fluorescence microscopy considered sensitive in detecting molecules?
It allows detection of single molecules
What are some examples of fluorophores mentioned in the context of fluorescence spectroscopy?
Tryptophan
Where does OH, CH2 and CH3 locate on the 1H-NMR spectrum of ethanol?
OH- downfield signal
CH2- midfield signal
CH3- upfield signal
What types of nuclei are typically analyzed using 1H-NMR spectroscopy?
Magnetically active hydrogen (1H) nuclei
What is the significance of Stokes shift in fluorescence spectroscopy?
It enables easier separation of excitation and emission photons.
What information can be obtained from a UV-Vis absorption spectrum?
The presence and concentration of substances
What do mass spectrometry measure & identify?
Molecular mass & identify unknown molecules & analyse molecular fragments
What does X-ray crystallography use and what is it used for?
Use x-ray diffraction patterns to determine 3D molecular structure
-Used for proteins & DNA structure analysis
