The essential resource that is available for investigating the molecular structure is the theory of molecular spectra. The discrete energy states of a certain molecule can be derived directly from the theory. Molecular energy levels and molecules in an excited state might seem more complicated to understand than atomic energy levels. This is because of the reason that molecules have the ability to rotate and vibrate. The energy which is associated with such motions of rotation and vibration lie in different ranges. You can study these different ranges separately to avoid complications and understand the subject matter easily.
[Image will be Uploaded Soon]
Spectroscopy or molecular spectroscopy is basically the area of science that deals with the emission, absorption, and scattering of electromagnetic radiation by molecules and atoms in phases such as solid, liquid, and gas. Spectroscopy also plays a crucial role in understanding the results of spectroscopic experiments and the development of the laws of quantum mechanics. The aim of spectroscopy is to make the discussion more concrete about the quantum mechanical description of the molecular properties and the laws of quantum mechanics.
Before you delve into understanding molecular spectroscopy in detail, first, you will need to get a solid understanding of the subject of the electromagnetic spectrum. It is because spectroscopy is defined as the scientific area that deals with the emission, absorption, and scattering of electromagnetic radiation by molecules and atoms. Visible electromagnetic radiation is termed light, although here, you can use the terms electromagnetic radiation, radiation, and light, interchangeably.
One of the essential aspects of physical chemistry is to recognize the interaction of molecules with the surroundings. With molecular spectroscopy, you can clearly imagine how a polyatomic and diatomic molecule interacts with its surroundings. Further, you can study how any polyatomic or diatomic molecule interacts when studying the wavelength, frequency, energy, wave number, and molecular process. The absorption properties of any polyatomic or diatomic molecule in different regions can also be seen from the electromagnetic spectrum.
Information of molecules is clearly provided by the electromagnetic spectrum about if there are electronic transitions, rotational transition, or vibrational transition. A molecule or a group of molecules is usually read by seeing the absorption of microwave radiation that provides transitions between energy levels which are rotational. Additionally, when a molecule or group of molecules can absorb infrared radiation, it can provide the transition between the vibrational levels, which is followed by the transition between rotational levels of energy.
Electromagnetic radiation is simply a form of energy. Waves and particles both describe the behaviour of electromagnetic radiation. The dual models involving wave and particle behaviour give us an informative description of electromagnetic radiation. Although, the exact nature of it still remains unclear since the development of the laws of quantum mechanics at the beginning of the 20th century.
Properties of Electromagnetic Radiation
When the refraction of electromagnetic radiation occurs, it passes from a medium to another, and it can be explained in the best way possible by describing light as a wave.
Properties like absorption and emission can be better explained when treating light as a particle.
Vibrational Transitions Accompanied by Rotations
While studying spectroscopy, it is important to know how each of the peaks of rotational transitions and vibrational transitions correlates with the molecular processes. In the first place, a molecule’s rotation is possibly affected by the molecule’s vibrational transition. This happens because of a change in bond length which is responsible for rotational transitions that might occur.
Now that we know the basics of spectroscopy look at some of the basic solved examples that will help you ace your exams.
Q1. Among the Options, Which One Can be Considered a Photographic Negative of an Emission Spectrum?
Option 1. Emission spectra
Option 2. Absorption spectra
Option 3. Atomic spectra
Option 4. Spectrum
Answer: Option 2. Absorption spectra
Q2. Choose the Term Which is Used for a Band of Colours.
Option 1. Spectra
Option 2. Spectral analysis
Option 3. Spectrum
Option 4. Dispersion
Answer: Option 3. Spectrum
Q3. Choose the One Which Is the Analysis of Electromagnetic Radiation.
Option 1. Spectroscopy
Option 2. Astronomy
Option 3. Kaleidoscopy
Option 4. Anatomy
Answer: Option 1. Spectroscopy
Q4. in an Atomic Emission Spectrum, Which One of These Lines is Present?
Option 1. Light
Option 2. Bright
Option 3. Brown
Option 4. Black
Answer: Option 2. Bright
Q5. Choose the One Which Has Lower Energy.
Option 1. Initial state energy level
Option 2. Excited-state energy level
Option 3. Ground state energy level
Option 4. None of these
Answer: Option 3. Ground state energy level