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Molekulaspektroszkopia
segédábrák
Az ábrák több, részben szerzői jogokkal védett műből, oktatási célra
lettek kivéve. Csak az intranetre tehetők, továbbmásolásuk,
terjesztésük nem megengedett.
Az ábrák csak illusztrációs célokat szolgálnak. Mivel többnyire más
szerzők műveiből származnak, olyan jelölések vagy állítások is
előfordulhatnak bennük, amelyekkel a tantárgy oktatói nem teljesen
értenek egyet.
"Heat“
Infrared radiation is popularly known as "heat" or
sometimes "heat radiation," since many people
attribute all radiant heating to infrared light, but this is
a widespread misconception. Light and
electromagnetic waves of any frequency will heat
surfaces which absorb them. IR light from the sun
only accounts for 50% of the heating of the Earth, the
rest being caused by visible light. Green (or even UV)
lasers can char paper and incandescently hot objects
put out visible radiation. However, it is true that
objects at room temperature will emit radiation mostly
concentrated in the 8-12 micron band (see black
body).
Die Wellenlänge der Ultraviolettstrahlung reicht von 1 nm bis
380 nm.
Die Frequenz der Ultraviolettstrahlung reicht also von 789 THz
(380 nm) bis 300 PHz (1 nm).
Die Energie eines einzelnen Lichtquants liegt im Bereich von
ca. 3,3 eV (380 nm) bis ca. 1000 eV (1 nm).
1 eV = 1,602 176 462(63) · 10-19 J
Ein typisches Molekül in der Atmosphäre hat eine Bewegungsenergie (thermische
Energie) von etwa 0,03 eV. Die Photonen von sichtbarem Licht (rot) haben eine
Energie von etwa 2 eV.
Boltzman-Konstante 1,38 · 10-23 J K-1 8,62· 10-5 eV K-1
Plancksches Wirkungsquantum h 4,14 · 10-15 eV s
Die ultraviolette Strahlung wurde 1802 von Johann Wilhelm
Ritter entdeckt.
Ultraviolet (UV) light is electromagnetic radiation
with a wavelength shorter than that of visible light,
but longer than soft X-rays. It can be subdivided
into
near UV (380–200 nm wavelength; abbrev. NUV),
far or vacuum UV (200–10 nm; abbrev. FUV or
VUV), and
extreme UV (1–31 nm; abbrev. EUV or XUV).
When considering the effect of UV radiation on
human health and the environment, the range of
UV wavelengths is often subdivided into UVA (400–
315 nm), also called Long Wave or "blacklight";
UVB (315–280 nm), also called Medium Wave; and
UVC (< 280 nm), also called Short Wave or
"germicidal".
Ordinary glass is partially transparent to UVA but is
opaque to shorter wavelengths while Silica or quartz
glass, depending on quality, can be transparent even to
vacuum UV wavelengths. Ordinary window glass passes
about 90% of the light above 350 nm, but blocks over
90% of the light below 300 nm[1][2][3].
The onset of vacuum UV, 200 nm, is defined by the fact
that ordinary air is opaque below this wavelength. This
opacity is due to the strong absorption of light of these
wavelengths by oxygen in the air. Pure nitrogen (less than
about 10 ppm oxygen) is transparent to wavelengths in
the range of about 150–200 nm. This has wide practical
significance now that semiconductor manufacturing
processes are using wavelengths shorter than 200 nm.
Copyrighted, 1998 - 2006 by Nick Strobel
www.astronomynotes.com.
Copyrighted, 1998 - 2006 by Nick Strobel
www.astronomynotes.com
Properties of Electromagnetic Radiation
Fig. 19-1, pg. 511 ”Plane-polarized electromagnetic
radiation of wavelength l, propagating along the x axis.
The electric field of the plane-polarized light is confined to
a single plane. Ordinary, unpolarized light has electric field
components in all planes."
Regions of
Electromagnetic Spectrum
Attenuation of Light
Grating vs. Prism
Beer's Law
Instrumental response
G = KP + K'
100% adjust, incident radiation
Go = 100 = KPo + 0.00
K = 100/Po
Spectronic 20
Double Beam Spectrometer
HP 8452a
Components of Optical
Instruments
Fig. 7-2, pg. 145 ”(a) Construction
materials
Components of Optical
Instruments
Fig. 7-2, pg. 145 ”(b) wavelength selectors for
spectroscopic instruments."
Components of Optical
Instruments
Fig. 7-3, pg. 146 ”(a) Sources."
Components of Optical
Instruments
Fig. 7-3, pg. 146 ”(b) detectors for spectroscopic
instruments."
Properties of
Electromagnetic Radiation
Fig. 6-2, pg. 118 "Effect of change of medium on a
monochromatic beam of radiation."
Properties of
Electromagnetic Radiation
Fig. 6-3, pg. 119 "Regions of the electromagnetic
spectrum"
Absorption of Radiation
Fig. 6-19, pg.134
"Some typical
ultraviolet
absorption
spectra."
Monochromator Slits
Construction of slits
Total Absorption
AT = A1 + A2 + A3 +  An
AT = e1bc1 + e2bc2 + e3bc3 + enbcn
Analysis of Mixtures of
Absorbing Substances
Selection of
Wavelength
Fig. 14-14, pg. 345
"Absorption
spectrum of a twocomponent
mixture."
Real Deviations
non-monochromatic
radiation
Fig. 13-4, pg. 305
"Deviations Beer's
Law with
polychromatic light.
Here, two
wavelenghts or
radiation l1 and l2
have been assumed
for which the absorber
has the indicated
molar absorptivities."
Real Deviations
Fig. 13-5, pg. 306
"The effect of
polychromatic
radiation upon the
Beer's law
relationship. Band A
shows little deviation,
because e does not
change greatly
throughout the band.
Band B shows marked
deviations because e
undergoes significant
changes in this
region."
Real Deviations
stray light
Fig. 13-6, pg. 307
"Apparent
deviation from
Beer's law brought
about by various
amounts of stray
radiation."
Single Beam vs. Double Beam
Fig. 13-12, pg. 315
"Instrument designs for
photometers and
spectrophotometers:
(a) single-beam design
(b) dual channel design
with beams separated in
space but simultaneous
in time
(c) double-beam design in
which beams alternate
between two channels."
Types of Transitions
Fig. 14-1, pg. 331 "Electron
distribution in sigma and pi
molecular orbitals."
Types of Transitions
Fig. 14-2, pg. 331 "Types of molecular
orbitals in formaldehyde."
Absorbing Species
Containing p, s, and n
Electrons
Fig. 14-3, pg. 331
"Electonic molecular energy levels."
s*
Antibonding
Antibonding
n
Nonbonding
s
s*
p*
p
s
Bonding
Bonding
UV Spectra
Fig. 14-4, pg.
334 “Ultraviolet
spectra for
typical organic
compounds.”
Visible Spectra
Fig. 14-5, pg 334
“Ultraviolet
absorption spectra
for 1,2,4,5tetrazine (a.) in
the vapor phase,
(b.) in hexane
solution, and (c.)
in aqueous
solution.”
Types of Transitions
Table 14-2, pg.
333 "Aborption
Characteristics
of Some
Common
Chromophores.
"
Types of Transitions
Table 14-3, pg. 355 "Effect of Multichromophores on
Absorption."
Interferogram vs. Spectrum
Qualitative Analysis
Fig. 17-4, pg. 408 Group frequency and fingerprint regions
of the mid-infrared spectrum.
Qualitative Analysis
Fig. 17-4, pg. 408 Group frequency and fingerprint regions
of the mid-infrared spectrum.
Qualitative Analysis
Fig. 17-4, pg. 408 Group frequency and fingerprint regions
of the mid-infrared spectrum.
Vibration Modes
Fig. 16-2, pg. 383
“Types of molecular
vibrations. Note: +
indicates motion from
the page toward the
reader; - indicates
motion away from the
reader.”
Potential Energy Diagram
Fig. 16-3, pg. 384 “Potential energy diagrams.
Curve 1, harmonic oscillator. Curve 2, anharmonic
oscillator.”
Infrared Sources
Most Common IR Sources
• Nernst glower
– cylinder of rare-earth oxides
• glowbar
– silicon carbide rod
– 50mm long by 5mm diameter
• incandescent wire
– nichrome wire
Infrared Detectors
• thermocouples
• pyroelectrics
Table 17-1, pg. 405
Major Applications of Infrared Spectrometry
Spectral
Type of
Type of
Regions
Measurement Analysis
Near-infrared Diffuse
Quantitative
reflectance
Absorption
Quantitative
Type
Samples
Solid or liquid
materials of
commerce
Gaseous
mixtures
Table 17-1, pg. 405
Major Applications of Infrared Spectrometry
Spectral
Regions
Mid-infrared
Type of
Type of
Measurement Analysis
Absorption
Qualitative
Type
Samples
Pure solid,
liquid, or
gaseous
compounds
Quantitative
Complex
gaseous,
liquid or solid
mixtures
Chromatographic Complex
gaseous,
liquid, or solid
mixtures
Table 17-1, pg. 405
Major Applications of Infrared Spectrometry
Spectral
Regions
Mid-infrared
Type of
Type of
Measurement Analysis
Reflectance
Qualitative
Emission
Quantitative
Type
Samples
Pure solid
or liquid
compounds
Atmospheric
samples
Table 17-1, pg. 405
Major Applications of Infrared Spectrometry
Spectral
Regions
Far-infrared
Type of
Type of
Measurement Analysis
Absorption
Qualitative
Type
Samples
Pure inorganci
or metal
organic
species
Sample Techniques
film
smear
sample cell
gas cell
KBr pellet
Nujol mull
internal reflectance apparatus
Deuterium lamps are gas discharge lamps filled with
Deuterium at carefully controlled pressures. They provide
a line free continuous UV spectrum from 180nm to 370nm,
Tungsten Halogen lamps (TH) are compact gas filled
filament lamps that provide a continuum output from 350nm
to 1000nm.
Emission spectrum of an ultraviolet deuterium arc lamp