Difference Between Average Relaxation and Molecular Relaxation Time

The key difference between average relaxation and molecular relaxation time is that average relaxation time describes the average time taken by a substance to return to its equilibrium state whereas molecular relaxation time is the time required to orient the dipolar molecules to the right direction.

In physical sciences, the term relaxation time refers to the time taken by a substance to convert into equilibrium from its perturbed state. In terms of chemistry, it explains the time interval between two successive collisions of electrons in a conductor material.

CONTENTS

1. Overview and Key Difference
2. What is Average Relaxation Time
3. What is Molecular Relaxation Time
4. Side by Side Comparison – Average Relaxation vs Molecular Relaxation Time in Tabular Form
5. Summary

What is Average Relaxation Time?

Average relaxation time is the average time taken by a substance to return to its equilibrium state. To be more specific, relaxation is the establishment of thermodynamic and statistical equilibrium in a physical system, and relaxation time is the time required for this process. Therefore, it describes the recovery of a perturbed system. Usually, relaxation is a multistep process. Therefore, it is very important to take the average of those relaxation steps to get an accurate value.

What is Molecular Relaxation Time?

Molecular relaxation time is the time required to orient the dipolar molecules in the right direction. This relaxation refers to the orientation of dipolar molecules in an alternating current system as dielectric relaxation. This parameter is measured using details about the relaxing system, its initial state, its final state, nature of the disturbance, and the response of the system.

For example, we can determine the molecular relaxation time for nitrogen tetroxide. Nitrogen tetroxide usually occurs in dimers. This means there are pairs of molecules. Therefore, it can easily dissociate into two molecules of nitrogen dioxide. Then the monomer is nitrogen dioxide. We can easily distinguish these two forms: dimer is colourless while monomer is a brown coloured gas. There is an equilibrium between these two forms. When this system is disturbed by a sudden change in temperature or pressure, these gases tend to reach a new equilibrium state. The time difference between the new equilibrium state and the initial equilibrium state is referred to as the molecular relaxation time.

What is the Difference Between Average Relaxation and Molecular Relaxation Time?

In physical sciences, the term relaxation time refers to the time taken by a substance to convert into equilibrium from its perturbed state. The key difference between average relaxation and molecular relaxation time is that average relaxation time describes the average time taken by a substance to return to its equilibrium state whereas molecular relaxation time is the time required to orient the dipolar molecules to the right direction.

To briefly describe the difference between average relaxation and molecular relaxation time, the average relaxation time describes the average recovery of a perturbed system, while the molecular relaxation time describes the conversion of one equilibrium state to another.

Summary – Average Relaxation vs Molecular Relaxation Time

In physical sciences, the term relaxation time refers to the time taken by a substance to convert into equilibrium from its perturbed state. The key difference between average relaxation and molecular relaxation time is that the term average relaxation time describes the average time taken by a substance to return to its equilibrium state whereas molecular relaxation time is the time required to orient the dipolar molecules to the right direction.

Reference:

1. Faller, Larry D. “Relaxation Phenomenon.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 11 Apr. 2016, Available here.
2. “Relaxation Methods.” Chemistry LibreTexts, Libretexts, 5 June 2019, Available here.
3. “Define Relaxation Time of the Free Electrons Drift Toppr.com.” Toppr Ask, 23 Oct. 2019, Available here.

Image Courtesy:

1. “Relaxation” By Creep.svg: Strafpeloton2derivative work: Bbanerje (talk) – Creep.svg (CC BY-SA 3.0) via Commons Wikimedia