LUMINESCENCE SPECTROSCOPY (11.0)

Question 1

optical method based on the measurement of photon by excited species

Answer 1

emission of radiation or luminescence

Question 2

provide info. on composition and amount of luminescent species

Answer 2

spectrum/ intensity released radiation

Question 3

4 features of luminescence (name)

Answer 3

1. inherent sensitivity (LOD = 1-3 orders of magnitude smaller than absorption,pbb levels
2. large linear conc. range
3. better selectivity than absorption spectroscopy
4. less widely applicable than absorption methods

Question 4

It is a type of luminescence that excitation is brought about through absorption of photons or radiation

Answer 4

fluorescence and phosphorescence

Question 5

It is a type of luminescence that excitation is brought about by chemical reaction, not by a radition source

Answer 5

chemiluminescence

Question 6

Electronic transition involves no change in electric spin (s excited to s ground)
also short lived (10^-5 s)

Answer 6

Fluorescence

Question 7

electronic transition involves a change in the electronic spin (from triple excited state to singlet ground state)
longer lifetime (10-4 - 10 s or longer); significantly less probable event than singlet/singlet transition

Answer 7

phosphorescence

Question 8

Fluorescence and absorption lines whose wavelength are identical

Answer 8

Resonance lines

Question 9

shift to longer wavelength for fluorescence lines or bands conpared with the absorption wavelengths

Answer 9

stroke’s shift

Question 10

rate of absorption

Answer 10

very rapid (10-14 to 10-15 s)

Question 11

slower rate; lifetime of excited state is inversely related to molar absortivities (10-3 to 5)

Answer 11

Rate of fluorescence and phosphorescence

Question 12

deactivation processes

Answer 12

favored route of ground state is one that minimize the lifetime of excited state (faster route); if deactivation by fluorescence is rapid with respect to radiationless processes emission is observed

radiationless path is faster, then fluorescence is absent or less intense

Question 13

DIFFERENT DEACTIVATION PROCESSES (PIEVI)

Answer 13

Vibrational relaxation 
internal conversion
external conversion
intersystem crossing
phosphorescence

Question 14

1. loss of excess vibrational energy through collision bet. excited species and molecule of solvent
2. energy transfer and slight inrease in temp of solvent
3. very efficient

Answer 14

VIBRATIONAL RELAXATION