What is metastable structure in metallurgy?

Metastable structures or, more accurately, configurationally frozen metastable structures are no novelty in metallurgy. However, in the past two to three decades we have seen a great upsurge in the production and study of new metastable structures in metallurgy, as well as in other condensed phase sciences.

What is metastable structure?

metastable state, in physics and chemistry, particular excited state of an atom, nucleus, or other system that has a longer lifetime than the ordinary excited states and that generally has a shorter lifetime than the lowest, often stable, energy state, called the ground state.

What does metastable mean in materials?

Metastable materials, or materials that transform to another state over a long period of time, are ubiquitous in both nature and technology and often have superior properties. Chocolate, for example, is metastable, with a lower melting point and better texture than stable chocolate.

What is the difference between metastable and unstable?

The mover will perceive his state of motion to be stable while his state of equilibrium is in fact metastable. For large challenges of balance, the mover may perceive his state of motion to be unstable while periodically approaching unstable states of equilibrium.

What is the meaning of metastable phase?

[¦med·ə′stā·bəl ¦fāz] (physical chemistry) Existence of a substance as either a liquid, solid, or vapor under conditions in which it is normally unstable in that state.

Why metastable state is important in laser action?

In a three-level laser, the material is first excited to a short-lived high-energy state that spontaneously drops to a somewhat lower-energy state with an unusually long lifetime, called a metastable state. The metastable state is important because it traps and holds the excitation energy, building up a…

Why metastable is important?

What are examples of metastable?

A ball resting in a hollow on a slope is a simple example of metastability. If the ball is only slightly pushed, it will settle back into its hollow, but a stronger push may start the ball rolling down the slope. Bowling pins show similar metastability by either merely wobbling for a moment or tipping over completely.

Can you obtain laser without metastable state?

Can you obtain the laser without metastable state? Answer from the author: Yes, there are laser gain media which do not have metastable states. This applies to semiconductor gain media and to laser dyes, for example.

Why there is a need for metastable state?

Metastable Meaning Due to this de-excitation process, the population inversion can not be achieved. Hence we need an intermediate energy level or the state where the atoms can stay a bit longer or atoms can have a longer lifetime.

Why metastable state is mandatory in laser operation?

What is metastable state in phase diagram?

Metastable phases undergo a phase transition as soon as a nucleus of a more stable phase (i.e., a less soluble phase) appears.

What is the meaning of metastable state?

See Article History. Metastable state, in physics and chemistry, particular excited state of an atom, nucleus, or other system that has a longer lifetime than the ordinary excited states and that generally has a shorter lifetime than the lowest, often stable, energy state, called the ground state.

Is metastable state a temporary energy trap?

A metastable state may thus be considered a kind of temporary energy trap or a somewhat stable intermediate stage of a system the energy of which may be lost in discrete amounts. In quantummechanical terms, transitions from metastable states are “forbidden” and are much less probable than the “allowed” transitions from other excited states.

What are metastable states in spectroscopy?

Analysis of atomic spectra often reveals metastable states as relatively final energy levels to which electrons have cascaded from higher energy levels in the act of generating light. Light energy trapped for a time in metastable mercury atoms accounts for the many photochemical reactions of this element.

What is the metastable state of a laser?

laser: Energy levels and stimulated emissions. …unusually long lifetime, called a metastable state. The metastable state is important because it traps and holds the excitation energy, building up a population inversion that can be further stimulated to emit radiation, dropping the species back to the ground state.