An Etymological Dictionary of Astronomy and Astrophysics
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Any of the several discrete states of energy which a particle, atom, or molecule can adopt under conditions where the possible values are restricted by quantum mechanical laws.

→ energy; → level.

A measure of the → energy of the least tightly held → electrons within a → solid at a → non-zero → temperature. The value of the Fermi level at → absolute zero (-273.15 °C) is called the → Fermi energy and is a constant for each solid. In other words, the Fermi level is any → energy level having the probability that it is exactly half filled with electrons in the → Fermi-Dirac statistics. Levels of lower energy than the Fermi level tend to be entirely filled with electrons, whereas energy levels higher than the Fermi tend to be empty.

→ Fermi; → level.

The → energy level which can be occupied by a → free electron in a → magnetic field.

→ Landau damping; → level.

A position with respect to a given or specified base. → energy level.

From O.Fr. livel, from L. libella "a balance, level," diminutive of libra "balance, scale."

Tarâz "level; a level," from tarâzu "balance, scales," Mid.Pers. tarâzên-, taraênidan "to weigh," Proto-Iranian *tarāz-, from *tarā- "balance, scale" ( cf. Skt. tulā- "scales, balance, weight," from tul- "to weigh, make equal in weight, equal," tolayati "weighs, balances," L. tollere "to raise," Gk. talanton "balance, weight," Atlas "the Bearer" of Heaven," Lith. tiltas "bridge;" PIE base telə- "to lift, weigh") + Av. az- "to convey, conduct, drive," azaiti drives" (cf. Skt. aj- "to dive, sling," ájati "drives," ajirá- "agile, quick," Gk. agein "to lead, guide, drive, carry off," L. agere "to do, set in motion, drive," from PIE root *ag- "to drive, move," → act).

Same as → significance level.

→ level; → significance.

The energy level adopted by a particle, atom, or molecule under quantum mechanical laws.

Occupied, p.p. of → occupy; → level.

The level of → Type I error which one is willing to risk in a → test of significance. Also called level of significance.

→ significance; → level.

The expression of sound intensity in decibel units. The sound intensity level (L_I), in decibels, is computed as: L_I = 10 log (I/I₀), where I is the measured sound intensity and I₀ is the reference intensity (1 x 10 ^-12 watt per square meter).

→ sound; → intensity; → level.

The sound energy emitted by a sound source per unit time and expressed in → decibels. Sound power, in → watts, is converted to sound power level in decibels (L), by L = 10 log (W/W₀), where W₀ is the reference power (1 x 10 ^-12 watt).

→ sound; → power; → level.

The splitting of a single atomic level into a group of closely spaced levels when the substance producing the single line is subjected to a uniform magnetic field. → Zeeman effect; → Stark effect.

→ spliting; → energy level.

In atomic physics, an initial energy state in an emission transition.

→ upper; → level.