Introduction to Spectrometry
光谱分析导论
(P201-203；270-272)

Spectroscopy is the use of the absorption,
emission, or scattering of electromagnetic
radiation by matter to qualitatively or
quantitatively study the matter or to study
physical processes. The matter can be
atoms, molecules, atomic or molecular
ions, or solids.
光谱分析方法的分类
分子光谱
原子光谱
紫外可见法
原子吸收法
红外法
光谱分析法
核磁法
原子发射法
荧光法
8.1 Electromagnetic Radiation（电磁辐射） and
Electromagnetic Spectrum（波谱）
光
是
一
种
电
磁
辐
射
（
电
磁
波
、
横
波
）
电场
磁场
传播方向
粒子性：光是由具有能量的光子组成，光子具
有质量和动能，每个光子能量
E  h 
Unit
hc



Relation to Meter
meter (m)
millimeter (mm)
1mm = 10-3m
micrometer (μm)
1μm = 10-6m
nanometer (nm)
1nm = 10-9m
Angstrom (Å)
1 Å = 10-10m

E2
E1
E  hc υ

Sometimes it is convenient to label the radiation
with the inverse（倒数）of the wavelength.
The inverse of centimeters (cm-1) is called the
wave number（波数）, and the unit is used
most often in infrared spectrometry. A
measurement made in wave numbers is often
denoted by υ . Then, the photon energy is the
product of hc and the wave number. That is,
电磁波谱（electromagnetic spectrum）
Electromagnetic -ray -ray ultraviolet visible infrared microwave radio
Wave
Wavelength
(nm) (nm)
10-3
to
10-2
10-2
To
10
(nm)
(nm)
(m)
(cm)
(cm)
10~380
380~780
0.78~100
0.1~1
10~
Example 8.1



What is the energy per photon of the sodium D
line (  589nm )?
Solution
The energy per photon of the sodium D line is
E 
hc


( 6 . 626  10
 34
J  s )  3  10 m  s
589  10
8
9
m
1
 3 . 37  10
19
J
8.2 Interaction of Electromagnetic
Radiation with Matter




Rotational movement 旋转运动
Vibrational movement 振动运动
Electronic movement 电子运动
Energy: discrete levels (quantization 量子化)
When an atom, ion or molecule changes energy
state, it absorbs or emits energy equal to the
energy difference  E = E1 - E0
Absorption EM
ground state
基态（E0） Transition 跃迁
excited state
激发态（Ei）
The wavelength or frequency of radiation absorbed
or emitted during a transition proportional to  E
Transition:
EM: E=h
equal to
ΔE = E1 - E0
Rotational Transition 转动跃迁 (0.005～0.050eV)
(100m~10cm; far-infrared; microwave; line spectrum)
 Vibrational Transition 振动跃迁 (0.05～1eV)
(2.5~15; 0.78~2.5m; mid-infrared; near-infrared)
 Electronic Transition 电子跃迁 (1～20eV)
(10~780nm; far-UV; near-UV; visible)
With molecules, we not only have
electronic but vibration and rotational
sub-levels. Interactions with other
molecules and a solvent will also have
an effect. These result in “band” spectra.

In atoms, there is a type of movement, i.e. electronic movement.
原
子
光
谱
分子光谱