Partition Functions

This post is part of a series,Nonsense and the Second Law of Thermodynamics. The previous post is entitled Fluctuations.

In previous posts it was shown that entropy is related to the the number of ways that a system can arrange itself subject to constraints such as constant energy.

The previous post on fluctuations showed that for very large numbers that fluctuation from the most probable distribution, are insignificant.  Most of the distribution is contained within the square root of N of the most probable result.

Thinking About Oil Rain

Recently, there has been discussion on the Internet of a video that purportedly shows evidence of it raining oil in Louisiana.



Is this evidence of oil rain? Is oil rain possible?

Infrared Spectra of Molecules of Interest

This post is part of a primer on infrared spectroscopy and global warming. The previous post concludes a three-post series that looks at molecules and radiation and discusses how molecules give rise to infrared spectra.  This post discusses the infrared spectra of some molecules of interest.

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Molecules and Radiation III: Vibration, Dipoles, and Ro-Vibrational Spectra

This post is part of a primer on infrared spectroscopy and global warming. The previous post looked at the vibrational modes of several molecules including HCl and several molecules of atmospheric interest. This post discusses how these modes relate to infrared absorption and uses HCl as an example.

Molecules and Radiation II: Molecular Vibration, Rotation, and Translation

This post is part of a primer on infrared spectroscopy and global warming. The previous post  starts the process of looking at the interaction between infrared radiation and molecules and discusses the degrees of freedom of molecules and the Born-Oppenheimer approximation.  The result of the previous post is that for the purposes of IR spectroscopy, one can focus on the motion of the atomic nuclei and separate them from the electronic degrees of freedom of a molecule.

Figure Source

There are 3N nuclear degrees of freedom for a molecule that has N nuclei.  For the HCl molecule that means there are 6 degrees of freedom.

Molecules and Radiation I: Molecular Structure

This post is part of a primer on infrared spectroscopy and global warming. The previous post  starts the process of looking at the interaction between infrared radiation and matter and discusses black-bodies and relationship between temperature and infrared radiation.  This post goes further and looks at how gas phase molecules interact with infrared radiation.

I

For a molecule to absorb radiation, several conditions must hold.  First, energy must be conserved: if the molecule absorbs energy from a photon, the molecule must be able to store that energy in some manner. 

A Primer on Infrared Spectroscopy and Global Warming

Introduction

This post and the posts linked to it through section headers together form a primer on infrared spectroscopy and how it relates to global warming.  The purpose of the primer is not be to convince skeptics that global warming is real, but rather to explain some of the terms and issues being discussed in climate science.  My goal is not to write a super technical explanation of infrared spectroscopy.  That's been done so many times that it is hardly worth doing again.

Rather, my intent is to write something that clearly describes infrared spectroscopy and relates it to global warming that tries to explain some fairly technical concepts in reasonably plain language.  As such there is an inevitable loss of fidelity about some of the fine points of infrared spectroscopy.  Anyone interested in such detail can follow some of the sources that I will provide.  At some point one has to compromise between accessibility and technical accuracy.  I hope that the choices made in this primer are helpful to some people trying to understand this topic.  This post is an outline of the topics addressed in the linked entries.

What is Infrared Radiation (IR)?

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This first post starts with the basics.  It discusses the electromagnetic spectrum and where infrared radiation fits into it.  It discusses waves and their measures.  It introduces the idea of electric dipole radiation.  It discusses the units of radiation wavelength, frequency. It ends by discussing photons and energy quantization.