约化普朗克常数，又称合理化普朗克常数，是角动量的最小衡量单位。 （念做h拔或者h bar）ℏ (ћ)=h/ (2π)

First, it is $h/2\pi$ rather than $h$ that appears in most formulas in quantum mechanics. We therefore define $$\hbar=\frac{h}{2\pi}=1.0546\times10^{-34}\,{\rm J\cdot s}$$ So basically it's just a matter of convenience.

唸為“h-bar”。 普朗克常數用以描述量子化，微觀下的 粒子 ，例如 電子 及 光子 ，在一確定的 物理 性質下具有一連續範圍內的可能數值。 例如，一束具有固定 頻率 ν {\displaystyle \nu } 的 光 ，其 能量 E {\displaystyle E} 可為：

2023年11月30日 · The main difference between h and h-bar is that h is the Planck constant, whereas ℏ (pronounced “h-bar”) is the reduced Planck constant, defined as h/2π. The Planck constant (h) and the reduced Planck constant (ħ) are fundamental constants in quantum mechanics and are often used in equations related to the behavior of particles at the ...

Planck's eponymous constant ℏ (pronounced h-bar) was introduced by Max Planck to explain experimental observations of the radiation spectra of black bodies. Planck's constant was broadened in meaning by Albert Einstein, who introduced the quantum of electromagnetic energy, now called a photon .

\hbar 是一个很少的常数，而跟据Correspondence Principle，量子理论在极限 \hbar \rightarrow 0 下，必需回归经典理论。 如果这不成立，这可能代表这现象是纯量子的（如entanglement），但更大可能这描述有错误。 这个Principle的例子很多，如光子的能量在极限 \hbar \rightarrow 0 下为零，即光的能量在经典极限下可看为连续的东西；又或 [x, p]=i \hbar \rightarrow 0，即在经典情况下，量度位移和动量的次序不重要。 （另可参Ehrenfest's Theorem） 很简单，就是为了方便计 …

2022年9月7日 · What is the difference between H and HBAR? A modified form of Planck’s constant called h-bar (ℏ), or the reduced Planck’s constant, in which ℏ equals h divided by 2π, is the quantization of angular momentum. For example, the angular momentum of an electron bound to an atomic nucleus is quantized and can only be a multiple of h-bar.

Planck's constant is usually written as h, but it's often useful to divide Planck's constant by , and then it is written , which is called h-bar: [math]\hbar = \frac{h}{2 \pi}.[/math] [2] The value of the Planck constant [3] is:

On the Answers.com page on Planck length, I see two almost-same formulas for the Planck length that differ only by the use of h and hbar. However, the constants are the same, and my calculator gives the correct answer for hbar instead of h, so the first use of h was probably intended to mean hbar.

And perhaps that's the most important quantity that has the units of h-bar. It's something that you should remember. Of h-bar has units of angular momentum, that's why when people talk about a particle of spin 1/2, they say the angular momentum is 1/2 of h-bar, and that has the right units.