Questions tagged [molecules]

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1answer
166 views

Solving linear response in frequency domain

My question stems from a derivation given in chapter 12 of R. McWeeny's Methods of Molecular Quantum Mechanics for solving linear response equations via variational perturbation theory. (Linear ...
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1answer
1k views

Can you make a metal denser by melting it and make it cool down under high pressure?

The answer is probably no. But can you make a metal denser by melting it and make it cool down under high pressure? Or would it just crack under internal stress when it returns to a solid? I'm going ...
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1answer
33 views

Why do we measure boiling point of a liquid in an opened vessel [closed]

Can't we measure the boiling point of a liquid in a closed vessel
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2answers
607 views

Implications of parity violation for molecular biology

In biology, the concept of parity emerges in the context of chiral molecules, where two molecules exist with the same structure but opposite parity. Interestingly, one enantiomer often strongly ...
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2answers
86 views

Is it possible to break a carbon dioxide molecule using electromagnetic waves?

I'm no expert in physics, but I was just wondering if breaking apart $\rm CO_2$ into oxygen and carbon would be possible using certain electromagnetic wave?
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0answers
124 views

Why can we see the fundamental rotational-vibrational transitions of molecules like CO?

In rotational-vibrational spectroscopy, the "fundamental" transition is the one in the lowest electronic state between the first vibrational level ($\nu'=1$) and the ground level ($\nu''=0$). Since ...
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1answer
99 views

Pair correlation function vs Bond length distribution of a van der Waal dimer

For a weakly bonded molecular dimer (when two atoms are interacting through van der Waal (vdW) interaction). Do the distribution of pair correlation function and vibrationally average bond-length ...
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1answer
40 views

Laser induced Ionization

We know that when a linearly polarised laser field interacts with a diatomic molecule ionization happens when the molecular axis is along the laser-field direction. However, in case of a circularly ...
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2answers
60 views

Infer material characteristics from atoms/molecules configuration [closed]

I'm not an expert in this field but I always wonder how deep is our knowledge about atoms and molecules from the point of view of the resulting material characteristics. The first example that comes ...
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2answers
59 views

If I'm using a compressor typically used for powering nail guns and other tools, why can't I make the air colder when I release it?

I've always been fascinated in learning how to make liquid air, and I learned that there is a branch called physical chemistry, which deals in the manufacturing of different chemicals. My question is, ...
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3answers
158 views

Is a mono-molecular spring possible?

I have seen and read a lot of springs being used in the macroscopic world, and I also know that things can behave differently on a much smaller scale. My question is could a single piece of molecules ...
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2answers
2k views

Why water molecules move faster when heated?

In his first lecture about the nature of Matter and Atoms, Professor Feynman claims that the higher the temperature of the steam gets, the quicker the movement of Water molecules will be. I don't see ...
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2answers
236 views

Is the molecular term ${}^1\Sigma^-$ possible in a molecule?

The old question How to understand this symmetry in the wavefunctions of a diatomic molecule? explores how it is possible for a quantum state to have zero angular momentum about a given axis (giving ...
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2answers
89 views

What does this notation mean: $\mathrm{O}_{2} \ \ a\,{}^{1} Δ_{g} ← X\,{}^{3}Σ^{-}_{g} $?

The notation (which I found in the abstract of this paper) is $$\mathrm{O}_{2} \ \ a\,{}^{1} Δ_{g} ← X\,{}^{3}Σ^{-}_{g}. $$ Any help with this? I understand it's talking about quantum states of ...
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4answers
1k views

Is water really $H_2O$? On a comment concerning the quantum mechanical description of water made by Hilary Putnam [closed]

I wanted to pose a question here (also posted to r/physics a bit earlier) and was hoping the you all might be able to help. I was re-reading a book by the philosopher Hilary Putnam titled Naturalism, ...
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2answers
42 views

How is the waveform deviation from the equilibrium related to the air molecule movement?

I'm not sure if this is a stupid question. I've been considering the deviation from the equilibrium reflects the air pressure, with larger deviations reflecting higher air pressure. But in Reetz and ...
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4answers
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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3answers
999 views

What's the lifetime of the excited state when you shine light on molecules?

Let's say, when x-ray hits a molecule, an electron from an inner shell absorbs the energy and flies away, so there's a hole waiting for an electron to come down and fill it. How long does this hole ...
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1answer
664 views

The “watering hole” frequency versus microwave oven frequency

I recently learned about the "watering hole," a group of frequencies between 1.42 and 1.66 GHz. I also read that microwave ovens operate at 2.4 GHz. If 21 to 18 cm (1.42 to 1.66 GHz) is the resonant ...
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1answer
27 views

Possible to predict the polarity of a magnet using only molecular analysis?

Is it possible to analyze the molecular arrangement of a magnet to predict which end is north? Or is it always a surprise until we see how it behaves near another magnet?
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1answer
192 views

Amount of heat energy required to cause dissociation of $H_2$ molecules [closed]

The minimum amount of heat energy required to cause complete dissociation of $n$ moles of $H_2$ gas at constant temperature $T$ is? Do I have to do anything with binding energy out here in this ...
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2answers
1k views

Why doesn't the ${\rm H}_2$ molecule have a permanent dipole while the neutral ${\rm H}\,{\rm\small I}$ has one?

According to the National Radio Astronomy Observatory, the $21\,{\rm cm}$ line of hydrogen can be emitted by the neutral hydrogen atom due to the magnetic interaction between the spins of the proton ...
6
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1answer
196 views

What are sigma and pi bonds in physics language?

Chemists often discuss sigma and pi bonds. To a physicist, it's not easy to figure out what these actually are, as discussions tend to be full of lots of chemistry jargon about "antibonding", "...
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5answers
115 views

If I replace water molecules with microscopic solid spheres, will they still reach the same height in communicating vessels?

I'm having an hard time understanding why liquids take the shape of the container or why they reach the same height in communicating vessels. I'm wondering if I try to simulate their behaviour in ...
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1answer
3k views

Degrees of Freedom of a Linear Triatomic Molecule

I was introduced to a formula for finding the DOF of a molecule which was 3N-k and i was told, it was just for translation and rotational degree of freedom. Here N is the no. Of atoms in that ...
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2answers
92 views

Small inter nuclear separation limit for Diatomic molecule

Let’s take the a simple $H_2^+$ molecule, where there is only electron which is $r_a$ away from the first proton and $r_b$ away from the other one. Let’s call the separation between the two protons $...
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1answer
157 views

Water molecules on the Sun? How does that work?

I've been reading about water on the Sun. The water they talk about is supposedly in a gaseous state because the Sun is so hot. But I'm wondering how even that could exist. Wouldn't the extreme ...
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4answers
578 views

Ammonia molecule as a two-state system: what if angular momentum is zero?

In the Feynman Lectures (III-8-6 and 9-1) there is a nice discussion of the ammonia molecule as a prototypical example of the two-state system in quantum mechanics. Feynman begins by saying he's ...
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3answers
110 views

Is there a theoretical size limit by ferromagnetic materials?

Hemoglobin contains 4 iron atoms and oxidized hemoglobin is diamagnetic.1 On the other hand iron-oxide nano particles can be ferromagnetic.2 I did not manage to find any reference about the size limit ...
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1answer
99 views

Electrically charged comb reacts to water

Correct me if this is wrong, if a negatively charged comb reacts to water(ex. tapwater), the water will bend towards the comb because the water molecule has a slight positively charged "side" and ...
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1answer
175 views

Electron Volts in Covalent Bonds of Nitrogen [closed]

(once again this question is not a duplicate of any other question to my knowledge, and this should actually help alot of people trying to ionize air) for one you can easily figure out that nitrogen ...
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2answers
1k views

Why isn't translational energy quantized?

I was reading over this article on spectroscopy/molecular energy levels: https://en.wikiversity.org/wiki/Spectroscopy/Molecular_energy_levels. It says that translational energy is not quantized. Is ...
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3answers
36 views

Can you increase kinetics energy if a molecule using something other then heat?

Is it possible ti increase the kinetic energy of a molecules using something other then heat? Is this possible but with ily certain molecules?
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1answer
688 views

Calculating binding energy of a molecule

To calculate binding energy of an atom we find difference between the mass of whole nucleons that constitute that atom and the experimental mass of the atom from tables. But, to calculate the binding ...
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2answers
629 views

Do molecules of liquid repel or attract each other?

Consider a liquid under the atmospheric pressure. Nonzero pressure inside the liquid means repulsion between molecules. On the other hand to explain the surface tension it is usually said that ...
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0answers
158 views

water dipole moment

I'm working my way through Halliday, Resnick, Walker's chapter on electric fields, and there is a solved sample problem (22-5, 8th ed.) about calculating the charge separation on a water molecule. ...
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3answers
7k views

How to understand the concept of degree of freedom?

I am not well versed in physics and it is being difficult to understand the degrees of freedom of a system. Question I know that degrees of freedom are movements in which a system - like a molecule ...
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1answer
225 views

If translational energy is a continuum, why molecules don't absorb any energy quantity?

I am just starting with quantum mechanics. Here an image where I show possible transitions but only should excite translational movement. Can a molecule absob ANY quantity of energy if it goes to ...
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1answer
55 views

High energy electron diffraction of molecules in the gas measures what?

For diffraction of an ensemble of molecules under suitable conditions, one can often read, that what one measures is a ensemble/thermal average of inverse distances, between scattering centers (atoms) ...
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1answer
334 views

Does a single molecule or atom have a density?

In a science lab I did recently we placed wax candles into two different liquids to see if they would float or sink. In one liquid, the candle floated, and the other one it sunk. We swapped the ...
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1answer
824 views

What is the physical significance of the overlap integral?

What is the physical significance of the overlap integral in the covalent bond formation (say, the $H_2$ molecule)? as far as I can understand, even if the overlap integral is zero, the Heitler-...
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1answer
234 views

Random motion of molecules

If we are given the initial position and the velocity of an object (ex. a ball) according to an inertial frame of reference we can calculate its position and velocity for another given time with high ...
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37 views

Current work on molecular manufacturing

How much work is currently being done on molecular manufacturing (a.k.a. Drexler-style nanotechnology)? Or for that matter, is any at all being done? A Google search has turned up some what-if papers ...
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1answer
125 views

Could an atom have a binary nuclei system?

I can't seem to find this answer anywhere online. I am trying to work through a solid state physics textbook for research and this popped into my head. I don't have any mathematical background on ...
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2answers
904 views

Does gravity have anything to do with Van Der Waal's forces?

Does gravity have anything to do with Van Der Waal's forces? Just throwing this out there, I was wondering if they do because gravity is such a weak force and the VdW forces at a molecular level could ...
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3answers
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Is it possible to obtain antiwater from antihydrogen and antioxygen atoms? And how is its property w.r.t. the ordinary water?

I am interested in experimental physics and looking for information about the above question.
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1answer
148 views

Which is the same between two connected rooms, relative or absolute humidity?

Question: Consider two glass bottles filled with humid air, connected with a tube. One of the glasses is hot (heated), the other is cold (cooled) and the situation is steady state. How will humidity ...
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0answers
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Determination of electromagnetic wave absorption by molecular vibration mode

In this physics.stackexchange answer, it is stated that the absorption of electromagnetic wave at a given wavelength by a molecule is determined by its vibration modes. What is the exact equation/...
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Partition Function for Molecules

I want to calculate the heat capacity for molecules in thermodynamics by using the partition function. I have given the Hamiltonian $ H = \frac{p_x^{2} + p_y^{2} + p_z^{2}}{4m } + \frac{p_\theta^{2}}{...
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1answer
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Negative or positive binding energy?

I'm working with modern physics atm, and can't seem to wrap my head around the binding energies of some molecules. At first, I thought that a negative binding energy = unstable molecule, and a ...