Difference b/w excited state and metastable excited sate?

In summary, an atomic or molecular state is conditionally stable, but will decay to the ground state if it collides with another atom that stimulates the transition.
  • #1
waqarrashid33
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difference b/w excited satate and metastable excited sate?and why the time period for m.s.excited state is greater than the common excited state?and how a photon deexite the electron when it is interacted with electron in m.s.excited state?



m.s.excite=metstable excited state
 
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  • #2
It is just a definition of a metastable state to be long-living.

Normally there are dipole transitions from excited states. For that the excited and the ground state should be different in dipole moment (different l, for example). But if the excited state does not have a dipole moment (l=0), the transition happens via quadrupole or two-photon mechanism which takes longer time.

Even a one-photon, dipole transition is not so easy, otherwise there will not be "excited" discrete states. A two-photon transition is even harder to carry out.

A one-photon transition is a transition between two different electron configurations, like from this | to this _ Obviously the electromagnetic filed should be emitted because the initial and final states create different electric configurations. But if the excited state is also like this _ , then a transition does not change much the electric filed, so there is practically nothing to radiate. This explains the "difficulty" in such transitions.
 
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  • #3
It usually means that the transition to a lower energy state is forbidden by quantum numbers, and can can only proceed via tunneling to another excited state which can decay to the lower energy state by an allowed transition. I think the 2S atomic state in hydrogen is an example.
Bob S
 
  • #4
sorry:
I m a student of F.Sc and in our course their is no datails about atomic structure,excitation,dexictitation only very minor details are given so please sir.BOB S discuss it simply and in detaile.
 
  • #5
An "allowed" atomic excited state has a lifetime, meaning the expected time before the excited state returns to the ground state by photon emission. Allowed state lifetimes depend on a complex formula for energy difference, wave function overlap, and quantum state parameters. For example, the calculated hydrogen 2p -> 1s allowed transition lifetime is about 1.6 nanoseconds. The hydrogen 2s-> 1s transition on the other hand, is not an allowed transition (called "forbidden"), and takes much longer to return to the 1s state. The quantum numbers are n, l, s, and m. Transition lifetimes from higher level hydrogen states are longer: 5p->1s is about 24 nanoseconds. These are all calculated and tabulated in Bethe and Salpeter, "Quantum Mechanics for One and two Electron Atoms", page 266. For higher Z hydrogen-like atoms, the lifetimes are shorter. Often, transitions with lifetimes over some arbitrary value, like 100 nanoseconds, are called metastable, even thought they may be "allowed"..
Sometimes, an atomic or molecular state is conditionally stable, but will decay to the ground state if it collides with another atom that stimulates the transition (like in a gas).
Bob S
 
  • #6
waqarrashid33 said:
difference b/w excited satate and metastable excited sate?and why the time period for m.s.excited state is greater than the common excited state?and how a photon deexite the electron when it is interacted with electron in m.s.excited state?
m.s.excite=metstable excited state

Hi
im sorry ... I completed my B.Tech 3 years back ... i forgot this topic...

http://www.platform-rentals.co.uk/
 
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1. What is the difference between the excited state and metastable excited state?

The excited state is a higher energy state of an atom or molecule than its ground state, which is the lowest energy state. The metastable excited state is a long-lived excited state that is higher in energy than the ground state, but lower than the excited state.

2. How do the lifetimes of excited state and metastable excited state differ?

The excited state typically has a shorter lifetime than the metastable excited state. This is because the excited state quickly decays to the ground state through the emission of a photon, while the metastable excited state can remain in its state for a longer period of time before decaying.

3. What causes an atom or molecule to enter the excited state or metastable excited state?

Atoms or molecules can enter the excited state or metastable excited state by absorbing energy, typically in the form of light or heat. This energy excites the electrons in the atom or molecule to a higher energy level, resulting in the excited or metastable state.

4. Can the excited state and metastable excited state be observed in everyday life?

Yes, both states can be observed in everyday life. For example, the light emitted from neon signs is due to the excited state of neon atoms. Metastable excited states can also be observed in certain types of light bulbs, lasers, and in some chemical reactions.

5. What is the significance of the excited state and metastable excited state in scientific research?

The excited state and metastable excited state play important roles in many scientific studies and applications. For example, they are essential in understanding the behavior of atoms and molecules, as well as in fields such as spectroscopy, laser technology, and plasma physics. They also have practical applications in areas such as lighting, chemical reactions, and medical imaging.

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