Spectroscopy

Question 1

A sample in a 1.0-cm cell transmits 80% light at a certain wavelength. If the absorptivity of this substance at this wavelength is 2.0, what is its concentration?

Answer 1

c = 0.050 g/L

Question 2

absorption FORMULA

Answer 2

A = -log T = log 1/T = log P0/P =abc

Question 4

Transmittance Formula

Answer 4

T = P0/P

Question 5

PERCENTAGE TRANSMITTANCE

Answer 5

%T = P0/P x 100

Question 6

amount of monochromatic radiation absorbed by a sample

Answer 6

Bouguer–Lambert-Beer’s law/
Beer’s Law

Question 7

study of the interaction of electromagnetic radiation in
all its forms with matter

Answer 7

spectroscopy

Question 8

Latin “spectron”

Answer 8

ghost/ spirit

Question 9

σκοπειν

Answer 9

to see

Question 10

Method involves in the interaction of light

Answer 10

excitation and detection

Question 11

TRUE OR FALSE

Electromagnetic radiation moves through a medium other than a vacuum with a velocity, v, less than that of the speed of light in a vacuum

Answer 11

TRUE

Question 12

Change in intensity I of incident light

Answer 12

ABSORPTION

Question 13

Excitation induces emission of light from the sample

Answer 13

EMISSION

Question 14

emission from excited electronic singlet states

Answer 14

FLUORESCENCE

Question 15

emission from excited electronic triplet states

Answer 15

PHOSPHORESCENCE

Question 16

light scattering involving vibrational transition

Answer 16

RAMAN SCATTERING

Question 17

Two types of spectrometers

Answer 17

DISPERSIVE
FOURIER TRANSFORM

Question 18

TRUE OR FALSE

A source of electromagnetic radiation must provide an output that is both intense and stable in the desired region of the electromagnetic spectrum.

Answer 18

TRUE

Question 19

A source that emits radiation over a wide range of wavelengths,
with a relatively smooth variation in intensity as a function of
wavelength

Answer 19

continuum

Question 20

emit radiation at a few selected, narrow wavelength ranges

Answer 20

LINE SOURCES

Question 21

TRUE OR FALSE

The ideal wavelength selector has a high throughput of radiation and a narrow effective bandwidth

Answer 21

TRUE

Question 22

Why is high throughput desirable?

Answer 22

because more photons pass through the wavelength selector, giving a stronger signal with less background noise

Question 23

provides a higher resolution, with spectral features separated by more than twice the effective bandwidth being resolved

Answer 23

narrow effective bandwidth

Question 24

The simplest method for isolating a narrow band of radiation

Answer 24

absorption or inference filter

Question 25

work by selectively absorbing radiation from a narrow region of the electromagnetic spectrum

Answer 25

ABSORPTION FILTER | piece of colored glass

Question 26

use constructive and destructive interference to isolate a narrow range of wavelengths

Answer 26

INTERFERENCE FILTERS

Question 27

more expensive, but have narrower effective bandwidths, typically 10–20 nm, with maximum throughputs of at least 40%.

Answer 27

INTERFERENCE FILTERS

Question 28

LIMITATIONS OF USING FILTERS

Answer 28

* Do not allow for a continuous selection of wavelength * Available for only selected nominal ranges of wavelengths

Question 29

have a diffraction grating to disperse the radiation into its component wavelengths

Answer 29

MONOCHROMATORS

Question 30

simultaneously allows source radiation of all wavelengths to reach the detector

Answer 30

INTERFEROMETERS

Question 31

The signal at the detector shows intensity as a function of the moving mirror’s position, expressed in units of distance or time

Answer 31

interferogram

Question 32

time domain spectrum is also called

Answer 32

interferogram

Question 33

convert a signal consisting of photons into an easily measured electrical signal

Answer 33

Modern detectors

Question 35

used for optical spectroscopy

Answer 35

Photon Transducers

Question 36

contain a photosensitive surface that absorbs radiation in the ultraviolet, visible, and near infrared (IR), producing an electric current proportional to the number of photons reaching the transducer

Answer 36

. Phototubes and photomultipliers

Question 37

used to calibrate the detector’s response, to amplify the signal from the detector, to remove noise by filtering, or to mathematically transform the signal

Answer 37

Signal Processors

Question 38

These have very high excitation energies and do not contribute to absorption in the visible or UV regions

Answer 38

Closed shell electrons that are not involved in bonding

Question 39

These also possess too high an excitation energy to contribute to absorption of visible or UV radiation

Answer 39

Covalent singlebond electrons

Question 40

These are less tightly held than σ electrons and can be excited by visible orUVradiation

Answer 40

Paired nonbonding outershell electrons

Question 41

These are the most readily excited and are responsible for the majority of visible and UV light absorption.

Answer 41

Electrons in π (pi) orbitals

Question 42

formed by head to head overlap of atomic orbitals

Answer 42

sigma bond

Question 43

strong and have a high bond energies

Answer 43

sigma bond

Question 44

can exist independently

Answer 44

sigma bond

Question 45

found in single, double and triple bonds

Answer 45

sigma bond

Question 46

the overlapping orbitals can be pure or hybrid

Answer 46

sigma bond

Question 47

formed by the side-to-side overlap of atomic orbitals

Answer 47

pi bond

Question 48

relatively weak

Answer 48

pi bond

Question 49

must exist along the sigma bond

Answer 49

pi bond

Question 50

found in double and triple bonds

Answer 50

pi bond

Question 51

the overlapping bonds must be unhybridized

Answer 51

pi bond

Question 52

The absorbing groups in a molecule

Answer 52

chromophores

Question 53

A molecule containing a chromophore

Answer 53

chromogen

Question 54

does not itself absorb radiation, but, if present in a molecule, it can enhance the absorption by a chromophore and/or shift the wavelength of absorption when attached to the chromophore

Answer 54

auxochrome | hydroxyl groups, amino groups, and halogens

Question 55

absorption maximum shifted to longer wavelength

Answer 55

bathochromic shift

Question 56

absorption maximum shifted to shorter wavelength

Answer 56

hypsochromic shift

Question 57

an increase in molar absorptivity

Answer 57

hyperchromism

Question 58

a decrease in molar absorptivity

Answer 58

hypochromism

Question 59

The amount of monochromatic radiation absorbed by a sample is described by

Answer 59

BEER'S LAW

Question 60

The relationship between the incident radiation and the transmitted radiation

Answer 60

TRANSMITTANCE

Question 61

The product of the absorptivity and the molecular weight of the absorbing species is called

Answer 61

molar absorptivity | A = εbc