Recent content by Quantum Defect

I guess I am with Borek. Lewis Electron Dot structures are a simplification for understanding the bonding in molecules. If you look at Lewis' original paper on the subject, he even proposes that the octet rule may have something to do with an atom being cubical, with electrons at the vertices...

Beer's law combined with a larger absorbance at short wavelengths, compared with longer wavelengths.

There is at least one typo: "... you are a year subscription to Physics Today..." I believe that one of the useful skills to begin to learn in the first year laboratory course is the ability to keep a good lab notebook. My first year physics lab instructor liked to give everyone a copy of a...

It helps to make these molecules with model kits. With your model of the molecule (or with one in your head), put dots of paint on two of the hydrogen atoms. If you can do some non-bond-breaking kind of motion to the molecule to take one form into the other [i.e. they are identical...

The first part of the counting the types of motion is the first part: 3 * N. This can be imagined as coming about by taking all possible combinations of the three cartesian directions on each atom. Imagine one possible motion has atom 1 move in the x direction, atom 2 move in the y direction...

The basic rule is: |<f|dipole operator|i>|2 < > 0 Where <f| is the final state, |i> is the initial state, and the dipole operator is sandwiched in between. Starting from this rule, you can use symmetry properties of the different kinds of rovibronic wavefunctions to come up with selection...

The second figure you link to shows a hydrogen spectrum where there is strong absorption at the line center. This is a single peak, where the top has been reduced in size due to the presence of cooler hydrogen between light source and observer. The depression at the center of the line makes...

You need to calculate the power incident on the planet from the sun. This can be approximated by the ratio of the cross sectional area presented to the sun (pi*r_planet^2) divided by the total area (solid angle) 4*pi*r_orbit^2 times the power output by the sun (assumes isotropic radiation). At...

We have all done things like this. :wink:

What is gamma? it should be the ratio of Cp/Cv, correct? Which is larger, Cp or Cv ? Should gamma be greater or less than one?

The sixth line means the sixth observed line. Here are the transisitons: n_i --> n_f 3--> 2 (first line) 4--> 2 (second line) 5--> 2 (third line) ... Which is the sixth line?

(1) Should be lots of measurements of the line. These measurements will be part of a bigger picture, though, like the article you link to -- they are using the line to infer other information. c.f. http://iopscience.iop.org/0004-637X/488/2/760/fulltext/fg3.gif which comes from...

It might help if you give us (and yourself) some examples of molecular solids. With these examples, think about what kinds of forces/bonding exist between the individual units.

What you are looking at is probably a list of periodic trends for the oxygen family hydrides (H2O, H2S, H2Se, etc...) As you move up the column, the boiling points decrease. H2S is a gas at room temperature, you would predict (based upon the trend) that H2O would also be a gas, and have an...

Whoops. You are correct, I mistook the 3p-2s for the one you were asking about. Here is a better source: http://www.nist.gov/srd/upload/jpcrd382009565p.pdf This source lists the transition (#73 in the list for He, on page 618) as being 1,344 cm^-1 -- in the infrared region.