C8785 Photophysical Spectroscopic Methods
Pavel Friš, Vít Ladányi, Ľubica Krausková, Gabriela Bičanová, Ján Krausko,
Lucie Ludvíkova,
Dominik Heger
Masaryk University hegerdQchemi. muni. cz
PSM 01 Intro
Pavel Friš, Vít Ladányi, Ľubica Krausková, G;C8785 Photophysical Spectroscopic Methods
1/16
PSM 01 Intro
Photophysics
Pavel Friš, Vít Ladányi, Ľubica Krausková, G;C8785 Photophysical Spectroscopic Methods
2/16
PSM 01 Intro
Photophysics
Pavel Friš, Vít Ladányi, Ľubica Krausková, G;C8785 Photophysical Spectroscopic Methods
PSM 01 Intro
2/16
Spectroscopy: Hydrogen emission and absorption spectra
Mk) 4000 5000 6000 7000
			
H11H H H  H H H H II IIH H H H			
			
UA) 4000 5000 6000
Johann Balmer (1885, Basel,Switzerland) Johannes Rydberg (1988, Lund, Sweden)
Pavel Friš, Vít Ladányi, Ľubica Krausková, G;C8785 Photophysical Spectroscopic Methods
PSM 01 Intro 3/16
C8785 Photophysical Spectroscopic Methods
The goal:
• Understand to spectroscopy, and measure well, gain self-confidence.
• Get an overview of the theory and experimental details at one place.
Pavel Friš, Vít Ladányi, Ľubica Krausková, G;C8785 Photophysical Spectroscopic Methods
PSM 01 Intro 4/16
C8785 Photophysical Spectroscopic Methods
The goal:
• Understand to spectroscopy, and measure well, gain self-confidence.
• Get an overview of the theory and experimental details at one place.
Content
9 Absorption - liquid, solid.
• Luminescecnce - steady state, time resolved.
• Transient absorption
Pavel Friš, Vít Ladányi, Ľubica Krausková, G;C8785 Photophysical Spectroscopic Methods
PSM 01 Intro 4/16
C8785 Photophysical Spectroscopic Methods - Lecture 01
O Spectroscopy
O Photophysics
O Transmittance, Reflectance, Absorptance, Absorbance
O Lambert-Beer-Bouguer law
O Foerster cycle
Pavel Friš, Vít Ladányi, Ľubica Krausková, G;C8785 Photophysical Spectroscopic Methods PSM 01 Intro 5/16
Physical quantities and their notation
Tabic /. /   The SI base quantities
Base	quantity		SI unit	
Name	Symbol tor	Symbol for	Name	Symbol
	quantity	dimension		
Length	/	L	metre	m
Mass	m	M	kilogram	kg
Time	!	I	second	S
Electric current	I	1	ampere	A
Thermodynamic temperature	!	e	kelvin	K
Amount of substance	n	N	mole	mol
Luminous intensity	/v	J	candela	cd
The value of a physical quantity Q can numerical value {Q} and a unit [Q]
Q ={Q}[Q]
Ex. / = 5 cm
be expressed as the product of a
Pavel Friš, Vít Ladányi, Ľubica Krausková, G;C8785 Photophysical Spectroscopic Methods
PSM 01 Intro 6/16
Scaled quantities Q/[Q
350
400
450 500
pH	c (acetic acid)/ mM	kobs / s 1	
		12b"	12 c"
4.92	8.14	(9.4 ±0.1) y 106 (2)	n.d.
4.75	1.00	(4.35 ± 0.50) x 106 (3)	(4.21 ±0.96) x 106(4)
4.52	0.32	(1.41 ± 0.17) x 106 (4)	(1.38 ±0.31) x 106 (4)
Pavel Friš, Vrt Ladányi, Ľubica Krausková, G;C8785 Photophysical Spectroscopic Methods
PSM 01 Intro 7/16
Definitions and Lambert-Beer-Bouguer law
-log (<žy<Ž>0) = -log z- = sob = A(X)
t= internal transmittance (transmission factor)
p = 0J0O reflectance (reflection factor)
a = 0J0Q= 1 - r absorptance (absorption faktor)
/specfro-'Baityil .t
É
©chromatic
Extinction — sum of absoptioiL,
Pavel Friš, Vít Ladányi, Ľubica Krausková, G;C8785 Photophysical Spectroscopic Methods
PSM 01 Intro 8/16
Lambert-Beer-Bouguer law
Lambert-Beer
_> jresta.rt;with ( DEtools ) : "with í plots ) : w_LLh (linalg) : > ode :=diff (F(z) , z] =-m(z> *F (z) ;
ode:=-^-F{z) =-m{z) F(z) az
> dsolve^ode,F{0)=F[)}JF(z) ) ;
F(z)=F0e°
> m: =1. 0 ; nsol: =dsolve ( {ode,Z (0) =10 } ŕtype=rLTĽmeiric, outpnt= listprocedure);
m := 1.0
nso! := [z = prffc(z) ... and pruch F{z) = pr<}Ľ(z) ... ľihI pniĽ
> odeplot(nsol, [zrFtz) ] ,0. .8};
10-9
7-S-
F 5-4 3-2-1 -
(2.1)
(2-j>
<   □   ►    < [f?  ► <   -Ž   ►        -Š       'O Q, O
Pavel Friš, Vít Ladányi, Ľubica Krausková, G;C8785 Photophysical Spectroscopic Methods
PSM 01 Intro 9/16
Limits of Lambert-Beer-Bouguer law
Conditions for validity of linear relation A = e * c * /
e Independence of attenuators
9 Homogenous distribution
• No turbidity
• Parallel rays
• Radiation being monochromatic
9 Incident flux must not influence the atoms of molecules - should be non-invasive probe (far from saturation or total absorption)
Pavel Friš, Vít Ladányi, Ľubica Krausková, G;C8785 Photophysical Spectroscopic Methods
PSM 01 Intro       10 / 16
Spectra
<□► < [f? ► < -e ► < -ž ►     -š    •o q, o
Pavel Friš, Vít Ladányi, Ľubica Krausková, G;C8785 Photophysical Spectroscopic Methods
PSM 01 Intro       11 / 16
General Scheme of Spectrometer
Entrance slit
Source
Absorption cell
A
Exit slit i I
Dispersing element
Detector
Display
□        ö ►   < s ►
Pavel Friš, Vít Ladányi, Ľubica Krausková, G;C8785 Photophysical Spectroscopic Methods
PSM 01 Intro       12 / 16
Infromation sources
J. Michael Hollas: Modern Spectroscopy
Klan, Wirz: Photochemistry of Organic Compounds, From Concepts to Practice
<□►    < [f? ►    <        ►    <  -Ž  ►        -Š       'o q, o
Pavel Friš, Vít Ladányi, Ľubica Krausková, G;C8785 Photophysical Spectroscopic Methods
PSM 01 Intro       13 / 16
Stokes shift
0
T:'
.LL.
'Ti
'i!'
j
2
1 0
4-
i y'
o'
Anti-Stokes ■ Wavenumber, v
Anti-Stokes Rayleigh
						
						
						
Stokes
Rayleigh
Stokes
J. Michael Hollas: ModerncSpectroscopy
Pavel Friš, Vit Ladányi, Ľubica Krausková, G;C8785 Photophysical Spectroscopic Methods
PSM 01 Intro        14 / 16
Franck-Condon Principle; Vertical excitation
Pavel Friš, Vrt Ladányi, Ľubica Krausková, G;C8785 Photophysical Spectroscopic Methods
PSM 01 Intro       15 / 16
Stokes shift
400 500
J_L
2.104-
1.10
0
0-ľ 0'-1
4.5    4.0    3.5    3.0    2.5 2.0
0-2
'■  V  ■ 0'-2
The spectral positions of the 0-0' bands of absorption and fluorescence usually do not coincide exactly. The difference is called the Stokes shift. The excited state is generally more polarizable and often more polar than the ground state. Solvent relaxation then stabilizes the excited state following Franck^Condon excitation, so that the 0-0' band of absorption is usually at higher frequency than that of emission. When the excited state is much less polar than the ground state, the 0-0' band of fluorescence may appear at higher frequency than that of absorption (anti-Stokes shift). Unfortunately, the term Stokes shift, is also used to refer to the gap between the band maxima of absorption and emission (see the footnote to fluorescence in Section 2.1.1), which may be much larger than the shift, between the 0-0 bands.
Photochemistry of Organic Compounds
Klán, Wirz:
Pavel Friš, Vrt Ladányi, Ľubica Krausková, G;C8785 Photophysical Spectroscopic Methods
PSM 01 Intro       16 / 16