Tag: Atomic physics
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What are Atom Traps?
Atoms that are cooled below a millikelvin can also be held in space with either static magnetic fields, laser fields, or a combination of a weak magnetic field and circularly polarized light. Atoms traps can be used to accumulate a large number of laser-cooled atoms; confine them for further cooling and use them for studies…
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The Principle & Application of Nuclear Magnetic Resonance (NMR)
Nuclear magnetic moments (along with electronic magnetic moments) precess (spin) when placed in an external magnetic field, B. The frequency at which they precess, called the Lamor precessional frequency, wL, is directly proportional to the magnetic field. When the magnetic moment μ is lined up with the field as closely as quantum physics permits, the…
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Spin Quantum Number
This property of atomic electrons was discovered through experimentation. The close observation of spectral lines revealed that each line was actually a pair of very closely-spaced lines, and what is referred to as fine structure was hypothesized to result from each electron “spinning” on an axis as if a planet. Electrons with different “spins” would…
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Bohr’s Correspondence Principle
Bohr’s correspondence principle states that predictions of quantum theory must correspond to the predictions of classical physics in the region of sizes where classical theory is known to hold. The classical sizes for length, mass, and time are on the order of centimeters, grams, and seconds and typically involve very large quantum numbers like can…
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Magnetic Quantum Number
The magnetic quantum number for an electron classifies which orientation its subshell shape is pointed. The “lobes” for subshells point in multiple directions. These different orientations are called orbitals. For the first subshell (s; l=0), which look like a sphere pointing in no “direction”, so there is only one orbital. For the second (p; l=1)…
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The Exclusion Principle
The exclusion principle states that no two electrons in an atom can have the same set of quantum numbers i.e. be in the same quantum state. Note, if this principle wasn’t valid, every electron would occupy the 1st atomic state (state of lowest energy), the chemical behaviour of the electrons would be significantly different and…
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Angular Momentum Quantum Number
A shell is made up of subshells. Subshells are regions of space where electron “clouds” are allowed to exist, and different subshells actually have different shapes. The first subshell is shaped like a sphere as illustrated in Fig 1.0(s) i.e. you can visualize it as a cloud of electrons surrounding the atomic nucleus in three…
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Principal Quantum Number
Symbolized by the letter n, this number describes the shell that an electron resides in. An electron “shell” is a region of space around an atom’s nucleus that electrons are allowed to exist, corresponding to the stable “standing wave” patterns of de Broglie and Bohr. Electrons may “leap” from shell to shell, but cannot exist…
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Yukawa Meson Theory of Nuclear Forces
In 1935 Yukawa proposed in his paper that there exist a meson field, that is, a field that is different from the electromagnetic field, whose quanta, the mesons have a finite mass, which is coupled to protons and neutrons in a manner analogous to the coupling of photons to charged particles. The exchange of these…