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10
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2answers
405 views

In counting degrees of freedom of a linear molecule, why is rotation about the axis not counted?

I was reading about the equipartition theorem and I got the following quotations from my books: A diatomic molecule like oxygen can rotate about two different axes. But rotation about the axis ...
1
vote
1answer
24 views

Shape of interface between molecules

Two seas do not mix, what are the characteristics of the interface? If we are trying to draw the molecules together, what would the interface look like?
1
vote
1answer
16 views

What is thermophoresis?

I read wikipedia article and I saw a bad youtube presentation on thermophoresis, however I don't have a clear insight about the subject. I assume the forces are basically Brownian molecular forces ...
0
votes
0answers
27 views

Difficulty in understanding Maxwell Boltzmann distribution in case on ions in a field

I learned that the velocity of molecules obey Maxwell Boltzmann (MB) distribution at a Temperature T. If I have ions of mass 'M' accelerated to 2eV in a specific region. As the ions are not ...
0
votes
0answers
7 views

debris removal by electrification

Often during the lifetime of equipment, there is debris or residue accumulation on surface of, for example nozzles. This material accumulation can be quite strong. What kind of forces are they ...
0
votes
1answer
25 views

Why toilet paper is softer in moist air? [duplicate]

After a hot shower,the air from the bathroom is full of water steam,right? How does the air affect the texture of the toilet paper?I mean,the toilet paper it seems to be softer,but why? Can someone ...
1
vote
1answer
165 views

Bimolecular recombination in few words

I'm making a short seminar about VERY broad topic of fullerenes in photovoltaics, but I'd like it to be educational (not just full of words hard to audience to make them think I'm smart). In one of ...
1
vote
1answer
49 views

Finding the approximate distance between molecules in a gas

I have a problem to understand why the below derivation can be used to find the distance between molecules: This example is an approximation. We are supposed to find the average distance between the ...
1
vote
1answer
118 views

Thermionic emission, delayed emission and predissociation

In molecular photodissociation, the thermionic emission, delayed emission and predissociation are the same? Otherwise, what is the difference between them? My question is not about the solids, but I ...
2
votes
0answers
37 views

Why is the activation energy of combustion so large compared with regular bonding?

I wanted to know why combustion requires an activation energy and I found this article (see this too). It says that molecular oxygen ground state is a triplet state (according to Hund's rules), and ...
0
votes
2answers
95 views

Resonate frequency of an object?

Below is a paragraph taken from the web site, physicsclassroom.com: It is often useful to think of these electrons as being attached to the atoms by springs. The electrons and their attached ...
0
votes
1answer
48 views

Along with electrons, do molecules also directly take in photon energy from a source?

Let's take a black object for example. When waves of light (whether from the sun or a lamp) come into contact with the object, is it just the electrons (not the molecules) of the object that directly ...
3
votes
3answers
190 views

What is the difference between the shapes of molecules with different isotopes

I'll explain my question on example of water molecule. Let us have three water molecules: normal water $H_2 O$, heavy water $D_2 O$ and semiheavy water $HDO$. Is there any difference between the ...
0
votes
2answers
44 views

How does infrared radiation increase temperature?

Temperature is proportional to the average kinetic energy of particles in a medium. When impinged by infrared radiation, what happens on the microscopic level that translates that EM wave into the ...
3
votes
3answers
57 views

Why do we say linear molecules only have 2 rotational degrees of freedom? Why does the third 'frozen' one not count?

It is possible to excite rotations around the axes perpendicular to the bond of a linear molecule. However, rotation around the axis along the bond of the molecule would require huge energies, due to ...
0
votes
2answers
197 views

Unknown magnetic moment of orthohydrogen

Conforming to present atomic physics, the two elementary particles in hydrogen atoms can have either parallel or antiparallel magnetic moments, and the energy differences between these two kinds of ...
0
votes
1answer
42 views

Meaning of “electrostatic” and “nonresonant laser” fields

I just read the following sentence: The molecule is subjected to an electrostatic field $E$ combined with a nonresonant laser field of intensity $I$, whose linear polarization is collinear with ...
0
votes
1answer
39 views

Problem with the Cooley-Numerov Method for Solving the Radial Nuclear Schodinger Equation in the Born-Oppenheimer Approximation

I have been trying to implement a solver for the radial nuclear Schodinger equation in the Born-Oppenheimer approximation using a similar method to R. J. Le Roy's LEVEL program[1]. I have as input a ...
1
vote
1answer
285 views

Why is the orbital angular momentum of a pi electron along the axis of two atoms' molecule one?

I'm reading quantum chemistry. The book says that the orbital angular momentum of a $\pi$ electron along the symmetry axis of a molecule made up of two atoms is $\pm 1$. I think this is a primary ...
1
vote
1answer
298 views

Wigner Threshold law in Photodetachment and Photoionization

I am writing this question here because I have a problem in understanding the Wigner Threshold law in Photodetachment and Photoionization. The Wigner Threshold Law is given by: $\sigma$=$E^{L+1/2}$. ...
0
votes
1answer
27 views

Detecting molecules in space?

http://www.forbes.com/sites/alexknapp/2012/02/24/nasa-detects-solid-buckyballs-in-space/ I refer to the above article, which mentions that buckyballs "far smaller than the width of a hair" were ...
2
votes
1answer
58 views

induction of van der Waals forces

Is there a way to maximize van der Waals forces between two materials, by electrifying one material, thus creating dipoles/instantaneous dipoles and thus creating stronger van der Waals forces? has ...
0
votes
1answer
30 views

If you compress air to a large enough pressure do new molecules form that have a large activation energy?

If you compress air to a large enough pressure do new molecules form that have a large activation energy?
4
votes
2answers
915 views

What is the resonant frequency of liquid water?

I learned it's not 2.45 GHz. But what is it, then? In my failure to find the real value, I'm starting to wonder: does it even make sense talking about a resonant frequency of water molecules?
0
votes
0answers
13 views

How do you calculate the optical contact bonding force of 2 1 meter by 1 meter perfectly flat surfaces?

Optical contact bonding is a phenomenon in which two perfectly flat surfaces will stick together, held purely by intermolecular forces. The trouble is, is there a way to calculate the pressure between ...
1
vote
1answer
42 views

How to calculate the potential energy of an $H_2$ molecule

From left to right, electron $e_1$, $e_2$ and proton $p_1$, $p_2$. $r_0=0.529nm$ The total energy is sum of energy require to bring each particle to its place. Take the place of $e_1$ is zero ...
5
votes
2answers
163 views

Extra vibrational mode in linear molecule

When calculating the number of vibrational modes for a molecule, the formulas differ for linear $(n = 3N - 5)$ and non-linear $(n = 3N - 6)$ molecules, where $n$ is number of modes and $N$ is number ...
0
votes
3answers
694 views

Potential energy curve for intermolecular distance

I'm trying to understand this curve better, but I can't quite figure out what "negative potential energy" means. The graph should describe a molecule oscillating between $A$ and $B$, however where ...
0
votes
1answer
34 views

Software to calculate electron binding energy of molecules?

I need to calculate the binding energies for the various electrons in a few different molecules (to determine an appropriate wavelength to selectively ionize them). Are there any software packages to ...
1
vote
1answer
36 views

Molecular orbital theory

What I have learnt : When two waves overlap in phase, the resultant wave formed had a greater amplitude than that of the two interfering waves. When they overlap out of phase then the resultant ...
1
vote
0answers
67 views

Finding Electronic Energy Levels by Representation Theory

Let $$u=\left( \begin{array}{cccc} c_1&c_2&c_3&c_4 \end{array} \right)^T$$ for $$\psi = c_1\psi_1 + c_2\psi_2 + c_3\psi_3+ c_4\psi_4$$ We assume that $<\psi_i|\psi_j> = \delta_{ij}$ ...
2
votes
1answer
44 views

Energy levels in molecules

I apologize in advance if this turns out to be a duplicate question. As far as I can understand, if you bring two or more atoms together their wave functions begin to interfere and, since there ...
0
votes
2answers
35 views

Molecules from atoms [closed]

Why does two oxygen atoms combine to form a molecule and not 3 or 4?Also why does one sodium and one chlorine atom combine to form NaCl while two chlorine atoms are required to combine with one ...
2
votes
2answers
8k views

How to estimate the physical size of a molecule?

I'm reading some chemistry-related papers that employ concepts of droplet evaporation. Since I am no chemist, I am wondering: How can I estimate the actual size of a molecule, say succinic acid? An ...
2
votes
2answers
62 views

Is molecular vibration just phonon modes for a single molecule?

I'm reading about Raman Scattering, of which a big part is measuring the energy lost to/gained from Molecular Vibrations. I wasn't totally clear on exactly what is "vibrating" in vibrational modes (is ...
21
votes
3answers
3k views

Why isn't the color of a molecule a combination of the colors of its component atoms?

I was watching a documentary on youtube regarding Quantum Physics when it introduced the wavelengths of light emitted. Did a bit more research over the internet and I believe I understand the gist of ...
0
votes
1answer
75 views

Is possible to create water? [closed]

Theoretically is relatively easy to create water, because it is formed by only the hydrogen and one oxygen molecules. I know that the oxygen and hydrogen is highly flammable, and to union the ...
0
votes
0answers
21 views

How did scientists even count the mole? It is an enormous number [duplicate]

Or did they estimate the number? After all, it is impossible to locate and contain precisely that much atoms. Or was it arbitrary?
2
votes
1answer
462 views

If the source of sound is vibration, why can't we “hear” a object whose molecules are vibrating?

According to our physics textbook, the source of sound is vibration. According to our chemistry textbook, substances in solid state have molecules vibrating in a fixed position. So why can't I hear my ...
0
votes
1answer
51 views

Why is the melting point of an object inversly proportional to pressure?

In my science book it is written that as the pressure increases the melting point of a solid decreases but i think that it is wrong as the pessure will make the molecules stick together instead of ...
2
votes
0answers
52 views

How did Lord Rayleigh find the volume fraction of argon to air?

In order to isolate for pure nitrogen, Lord Rayleigh and his colleagues took some air and removed oxygen, carbon dioxide, and water vapour, leaving behind what he believed to be pure nitrogen. In ...
2
votes
2answers
112 views

To what fraction of the speed-of-light has any multi-atom molecule (or polyatomic ion) been accelerated?

Of course photons go $c$ in a vacuum, and seems there's data on electrons getting to $0.999999999976c$ and protons to $0.99999912c$. For the twins paradox to be plausible, one of the twins must ...
0
votes
0answers
49 views

What is the largest atom with a reliable configuration-interaction (CI) calculation?

The simplest approximation for calculating the ground state of an atom is the Hartree-Fock approximation. To get accurate result for the ground state energy, one has to do configuration-interaction ...
1
vote
1answer
101 views

How much am I floating above the chair I am sitting on? [duplicate]

The electrostatic repulsion between me and the chair keeps me hovering above the chair at all times. What is the average distance that exists between any two everyday object due to electrostatic ...
2
votes
0answers
46 views

Why is the water diamagnetic?

I checked using my permanent magnet that water is diamagnetic. But why is it like that? Does this have any important consequence for life?
3
votes
1answer
51 views

Why is the photoelectric absorption coefficient finite at the threshold frequency?

I mean the photoelectric effect of the hydrogen atom. It is weird. By the Fermi golden rule, the transition or absorption rate is proportional to the density of the final states. At threshold, the ...
1
vote
1answer
85 views

Physics involved in the DNA-structure discovery

In 1962 Francis Crick, James Dewey Watson and Maurice Hugh Frederick Wilkins won the Nobel Prize: For their discoveries concerning the molecular structure of nucleic acids and its significance for ...
15
votes
3answers
1k views

Why is the bottom part of a candle flame blue?

What’s the explanation behind the bottom part of a candle flame being blue? I googled hard in vain. I read this. I don’t understand how it’s explained by the emission of excited molecular radicals in ...
2
votes
2answers
85 views

How do atoms in a solid “communicate” force to each other?

What is the mechanism that carries and communicates force in a solid, on the atomic level? Is there some other mechanism besides atomic deformation and proximity? That is, if I had an infinitely ...
0
votes
2answers
140 views

Why is the spectrum of a blue flame the way it is?

In the spectrum of the blue part in a candle flame, there’s a violet emission at 432 nm due to excited CH* molecules (chemiluminescence). Why 432? Why not 400 or 500? There are emissions at 436, 475 ...