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.

OPINION: Don't Call Climate Doubters Deniers

I am friendly with  and love people who doubt the reality of climate change.  The same cannot be said for those who "doubt" the reality of the Final Solution.  Lately it has become commonplace to refer to the former as "deniers," but the implicit connection to the latter offends me.  To understand why, I think it is useful to look at these groups of people.

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.

Does Secondhand Smoke Kill?

By now everyone knows that smoking can kill, but does secondhand smoke really kill and how do we know that?

The National Institute of Health (NIH) has a good resource on Secondhand Smoke, and it is perhaps a good place to start. The NIH starts with a very general description from the National Cancer Institute:

You don't have to be a smoker for smoking to harm you. You can also have health problems from breathing in other people's smoke. Secondhand smoke is the combination of smoke that comes from the burning end of a cigarette, cigar or pipe and the smoke exhaled by the smoker. Secondhand smoke contains more than 50 substances that can cause cancer. Health effects of exposure to secondhand smoke include lung cancer, nasal sinus cancer, respiratory tract infections and heart disease.  There is no safe amount of secondhand smoke. Children, pregnant women, older people and people with heart or breathing problems should be especially careful.

Figure Source

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.