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Questions tagged [molecules]

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2answers
57 views

Why does water flow downhill?

Researching this topic, I found everyone just saying because of gravity. But that makes no sense to me. Gravity exerts a downward force: But water flowing downhill goes sideways. There must be a ...
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1answer
59 views

Completely forbidden transitions

$\newcommand{\bra}[1] {\left< #1 \right|} \newcommand{\ket}[1] {\left| #1 \right>} $In molecular physics and spectroscopy physicists often calculate the dipole transition elements between two ...
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1answer
37 views

What kind of molecular bond holds the H$_2^+$ molecule together? [on hold]

The H$_2^+$ molecule consists of two hydrogen nuclei and a single electron. What kind of molecular bond holds this molecular together?
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0answers
39 views

Is water molecule too small to apply tennis racket effect? [on hold]

Imagine a water molecule moving in empty space without interference from the surrounding, it has angular momentum and since the 2 hydrogen atoms only share 1 electron each the remaining electrons from ...
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2answers
737 views

How do molecules absorb heat?

How do molecules absorb and retain heat, and how is that heat able to still affect nearby molecules? On Venus there is a green-house effect where the large, dense Carbon-Dioxide atmosphere absorbs ...
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2answers
60 views

Degrees of freedom of a molecule

We all know that if we consider a mono-atomic molecule, it has $3$ translational degrees of freedom only, along the $3$ principal coordinates of the Cartesian coordinate system. In case of a ...
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1answer
50 views

What do we see when we observe a molecular orbital?

My understanding is that when two hydrogen atoms bond (for example) the wavefunctions describing each atom combine into a single molecular wavefunction. Assuming the Copenhagen interpretation, does ...
2
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1answer
110 views

Has any scientist actually seen a $H_2O$ molecule vibrate?

Has any scientist experimentally confirmed that H2O molecules vibrate when heat energy is provided to them? Maybe by passing X-Rays through them or by some special camera...?
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2answers
121 views

Van der Waals forces & Partial charges

We're told that charge is quantized. That the charge any body carries has to be an integral multiple of the fundamental unit of charge: $e=1.602×10^{-19}C$ such that $q=ne$ where $n$ is an integer. ...
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0answers
33 views

Law of equipartition of energy, shouldn't kinetic energy per molecule by $(3/2)kT/f$

I study that according to the law of equipartition of energy the average kinetic energy associated with each degree of freedom is equal to $(1/2)kT$. But shouldn't it be $\frac{(3/2)kT}{f}$ where $f$ ...
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3answers
9k views

Book recommendation for Atomic & Molecular physics

What are some interesting books for a sophomore undergrad about Atomic & Molecular Physics?
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3answers
147 views

Do proteins interact through classical or quantum mechanics?

For the protein interactions that occur in our cells, do they "follow" classical mechanics or quantum mechanics when interacting? I have zero knowledge about quantum mechanics, but I was wondering ...
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0answers
21 views

Vector components for the dipole of water

I was looking online for the components for the dipole moment vector of water in the molecular frame. Does anyone know what the values would be for $\mu_x$, $\mu_y$ and $\mu_z$ for a water molecule in ...
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1answer
114 views

How is temperature related to quantum vibrational states of molecules?

When a molecule of greenhouse gas absorbs a photon of long wave infrared radiation it is boosted to the next allowed vibrational state. The vibrational state, as I understand it, involves deformations ...
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0answers
43 views

What's the most likely mass for ethanol?

I am interested in learning a little about mass defect and calculating the molar mass of ethyl alcohol. I found this table of atomic weights and would like to use it to compute the mass of the ...
2
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2answers
57 views

How do molecules gain kinetic energy from light?

I know that molecules can absorb light through electronic and vibrational excitations, which certainly increase the internal energy of a molecule. This idea is always connected to the quantum theory ...
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4answers
96 views

Is the oxygen molecule $O_2$ fermion or boson?

I ask something makes me confused. In generating singlet oxygen molecule, I initially thought a light (photon) can excite the ground state oxygen molecule. However, my colleague said that process is ...
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0answers
40 views

Design and construction of a system identifying molecular nitrogen and water

I have read papers that use LIDAR-like and LIDAR-Raman systems that detect elements. I want to measure the vapor water ($\rm H_2O$) and $\rm N_2$ of trees/agriculture using Arduino and low cost ...
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0answers
45 views

Can we hold atomic hydrogen for a long time? [closed]

If we take atomic hydrogen with similar spin together, can we hold it in balloon? I know, that the atom is hydrogen is reactive. But when all atoms will have similar spin, reactions between them will ...
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2answers
66 views

How do you define volume for gases? [closed]

Straight forward question. If atoms forming a gas float far from each other, how can we assign a volume to it? if it is in a container, perhaps we'd say the atoms, or molecules, reach every corner and ...
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0answers
15 views

Transition Dipole Moments and Quantum Yield

I'm using some DFT calculations to compute Transition Dipole Moments between the HOMO and LUMO of a molecule in different geometries. Intuitively, this is closely related to the relative probability (...
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3answers
2k views

Are there exact analytical solutions to the electronic states of the hydrogen molecular ion $\mathrm H_2^+$?

The hydrogen molecular ion (a.k.a. dihydrogen cation) $\mathrm H_2^+$ is the simplest possible molecular system, and as such you'd hope to be able to make some leeway in solving it, but it turns out ...
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8answers
6k views

Can a single molecule have a temperature?

A show on the weather channel said that as a water molecule ascends in the atmosphere it cools. Does it make sense to talk about the temperature of a single molecule?
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2answers
1k 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: $\sigma$=$E^{L+1/2}$. ...
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0answers
10 views

Where does the energy go that is associated with a shift in a FRET spectrum (Forster Resonance Energy Transfer)?

In the commonly used Jablonski energy diagrams, some sort of loss during resonance energy transfer is usually indicated via horizontal lines below the excited state energy of the oscillator (see for ...
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0answers
12 views

Does emission-spectrum of molecule equal sum of emission-spectrum of its components

Imagine a number of elements with known emission-spectra, that form a primary chemical bond of either * ionic * covalent * metallic type. Does the emission-spectrum of the resulting molecule match the ...
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1answer
52 views

Different energy levels in quantum mechanics

I have a doubt regarding energy levels. I saw that translational energy levels are quasi-continuous, rotational energy levels are discrete and vibrational energy levels are more discrete. I want to ...
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0answers
30 views

Average position in the Morse potential

Does anyone know the analytical expression for $\langleψ_n|x|ψ_n\rangle$ in the Morse potential? In other words, I'd like to find the average position of a particle at the $n$-th vibrational level in ...
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1answer
34 views

Newtons laws of motion. Tension force

What is the difference between tension and the force that we apply externally. Also when we apply force externally let's say on moleculeA ( connected to other molecules through springs) then by newton ...
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0answers
20 views

Which bonds are broken when we use high laser energy?

If we suppose as in the picture that a laser with high energy been used to break down the bounds, what exactly happens? Is there anything to do with molecular orbitals? or?
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0answers
11 views

Is there a way to calculate the molecular ionization energy from the single atom ionization energies?

Let us call the ionization energies of three atoms $E_1, E_2 $ and $E_3$. Is there a way to at least approximate the ionization energy of the molecule formed by those three ionization energies?
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1answer
131 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 ...
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1answer
56 views

Are metals more reflective at lower temperatures? [duplicate]

I understand that when metal gets hot it loses its reflective properties, but does that also mean that the colder the metal is the more it reflects?
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1answer
41 views

Are individual atoms inside a molecule (covalent) still really EM neutral?

I am not asking about ionic bonds. I am in this case asking about covalent bonds. I have read this question: Why do atoms repel when closer but attract when farther apart? Where Swike says: ...
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1answer
34 views

How sound absorption results in heat?

When sound passes through a medium (say, air) and hits the boundary atoms/molecules of another medium (say, a solid) ...... How would you continue the story ? What happens at the interface in cases ...
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1answer
27 views

How will a polar molecule affect another molecule nearby, why it feels a relatively large force?

Mean position of the negative charges and positive changes are not at the same point (polar molecule) how will that affect another molecule nearby, why it feels a relatively large force? Will the type ...
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2answers
1k views

Degrees of freedom of a three dimensional polyatomic molecules

So the exact question is An ideal gas consists of three dimensional polyatomic molecules. The temperature is such that only one vibrational mode is excited. If $R$ denotes the gas constant, then ...
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0answers
42 views

Preconditioning self-consistent iteration

Publication arXiv:0804.2583 describes a method for doing self-consistent iteration without having to diagonalize the Hamiltonian operator at every step. IX. PRECONDITIONING As already ...
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0answers
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Reference for the electronic levels of the nitrogen atoms resulting from the dissociation of the nitrogen molecule

I would like to know a book or paper that makes a detailed description of the electronic levels of the nitrogen atoms, N+N, resulting from the dissociation of the nitrogen molecule, N$_2$, also at a ...
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6answers
13k views

How is water heavier than petrol, even though its molecular weight is less than petrol?

Molecular weight of petrol is so much higher than water, but when it comes to physical property, weight, one litre of water weighs more than one litre of petrol. How is it possible?
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1answer
47 views

Is the sun required for evaporation?

I understand that the sun would heat up a pool of water causing the overall temperature to increase. This would also mean that more molecules would have enough energy to escape the pool, but wouldn't ...
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0answers
18 views

Do delocalized electrons have different energies?

Consider a molecule with alternating single and double bonds between carbon atoms, such that multiple resonant configurations are possible, e.g. beta-carotene. While using UToko's edx course about ...
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1answer
58 views

Vibrations in Stones and Crystals [closed]

I have read studies done that indicate certain sounds can either disrupt or reinforce the molecular structure (I think this is the terminology used) of living organisms. This is based on the idea that ...
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0answers
39 views

Incompatibility between the Bohr-Sommerfeld quantization condition and the Dunham expansion

I'm trying to apply the RKR (Rydberg-Klein-Rees) method which computes the classical turning points, $a(E,J)$ and $b(E,J)$ of a diatomic molecule for a rotational-vibrational energy value E, and ...
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3answers
4k views

Potential energy curve for intermolecular distance

(source: a-levelphysicstutor.com) 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 ...
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0answers
55 views

How do gaseous molecules arrange themselves in liquids when they are “dissolved”?

To provide some context, I am trying to understand in better detail how oxygen from the lungs passes through a membrane and enters the vasculature in order to be transported via blood. I have ...
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1answer
26 views

Binding energy of a molecular ion?

The protons in the $\text{H}_2^{+}$ molecular ion are $0.106 \, \mathrm{nm}$ apart, and the binding energy of $\text{H}_2^{+}$ is $2.65\,\mathrm{eV} .$ What negative charge must be placed halfway ...
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2answers
81 views

Why is gaseous carbon dioxide transparent? [closed]

Some carbon-heavy products of combustion, e.g. soot, are black, as is carbon in other forms, e.g. graphite. This seems to suggest that carbon is black. But then how can $\text{CO}$ (carbon monoxide) ...
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1answer
48 views

When a diatomic ion dissociates, how does the electron density on each atom change?

Let's say, we have a fluorine molecule (F2), and we take 3 electrons from it, so now its bond starts to stretch, and at last the bond breaks and the two atoms are farther and farther away from one ...
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0answers
21 views

Branch of Physics that Examines Atoms Relationships

Is there a specific branch of physics that can examine and calculate the strengths of atomic or molecular bonds and predict how they are going to break, putting into consideration the surrounding ...