---
title: "磁场为什么会把一条谱线分开"
description: "Zeeman 看见的谱线和 Lorentz 预言的偏振，怎样相互印证？"
canonical_url: "https://sandboxphysics.com/zh/stories/quantum-evidence/zeeman-lines-polarization-lorentz/"
language: "zh-CN"
page_type: "story"
alternate_languages:
  en: "https://sandboxphysics.com/stories/quantum-evidence/zeeman-lines-polarization-lorentz/"
last_modified: "2026-10-24"
---

[量子物理：读懂证据](https://sandboxphysics.com/zh/stories/quantum-evidence/)

诺奖 A · 证据与操控

# 磁场为什么会把一条谱线分开

Sandbox Physics · 2026-10-15

Zeeman 看见的谱线和 Lorentz 预言的偏振，怎样相互印证？

## 把发光的物质放进磁场

把发光物质送出的光分开，会看到一条条明亮的谱线，每条线对应一种颜色。1896 年，Zeeman 在荷兰莱顿研究磁场能否改变这些颜色。他把光源放在磁极之间，比较磁场打开和关闭时的光谱。最初引人注意的变化，是原来很窄的谱线变宽了。

这件事发生在光发出的地方。磁场影响了发光物质里的运动，光谱随之改变。Zeeman 在 1897 年报告了观测，并请 Lorentz 帮助解释。两人后来共同获得 1902 年诺贝尔物理学奖。

证据阅读：P. Zeeman (1897), The Effect of Magnetisation on the Nature of Light Emitted by a Substance, Nature 55, 347 P. Zeeman (1897), original Nature report — University of Maryland scan Nobel Prize in Physics 1902 — official award record

## 宽线里面还有方向

一条线变宽，原因可能很多。温度升高会让原子运动更快，碰撞也会扰乱发光过程。Lorentz 的理论给出了更具体的预言：在磁场中运动的带电粒子，沿不同方向振动时，频率会发生不同变化。原来重在一起的颜色，便可能分开。

光的振动方向叫偏振。Lorentz 预言，沿着磁场看，谱线两侧的光应当分别带有相反的圆偏振：光的振动方向绕传播方向旋转。从侧面看，则应出现不同的线偏振分量。Zeeman 用偏振观测检验了这个预言；谱线的宽度、观察方向和偏振终于能放进同一个解释。

在后来常用的理想三重线图景中，从侧面可看见中央一条和两侧两条：中央光的振动平行于磁场，两侧垂直。沿磁场看，中央分量不出现。观测方向换了，可见的分量也跟着换。

证据阅读：P. Zeeman (1897), The Effect of Magnetisation on the Nature of Light Emitted by a Substance, Nature 55, 347 P. Zeeman (1903), Light Radiation in a Magnetic Field — Nobel lecture, University of Maryland copy NIST Atomic Spectroscopy, Zeeman Effect — weak-field energy shifts and magnetic factors

## 今天把它读成能级的分裂

按现代原子图景，原子只能取某些能量，称为能级；从较高能级跳到较低能级时，能量差以光的形式放出。磁场改变了能级，一条原先重合的跃迁就可能分成几条，光的颜色也随之略有差别。

弱磁场里，某个磁子能级的位移可写成下式。磁场强度是 B；玻尔磁子把磁场换算成能量；磁因子和投影量子数描述这个态的磁响应。实际谱线的位移要比较跃迁两端的能量变化。公式适用于原来角动量标记仍有效的弱场情形。

$$
\Delta E=g_J\mu_{\mathrm B}m_J B
$$

证据阅读：NIST Atomic Spectroscopy, Zeeman Effect — weak-field energy shifts and magnetic factors

## 经典解释的成功，和后来的新问题

最简单的正常三重线，Lorentz 用经典带电振子就解释得很好。当时的成功很具体：他把磁场、颜色和偏振连了起来。把所有磁场分裂都讲成量子力学一开始就战胜经典理论，会错过这段历史。

后来出现的复杂分裂图样，需要电子自旋等新的原子结构知识。磁场足够强时，原子内部原有的耦合也会改变，弱场公式的线性关系随之失效。今天读 Zeeman 的实验，可以先记住最初那一步：除了看颜色偏了多少，还要问从哪个方向看，光怎样振动。

证据阅读：P. Zeeman (1903), Light Radiation in a Magnetic Field — Nobel lecture, University of Maryland copy Nobel Prize in Physics 1902 — official award record NIST Atomic Spectroscopy, Zeeman Effect — weak-field energy shifts and magnetic factors

## 接着操作模型

下面这些教学 Lab 产生的是模拟数据，和上文讨论的历史观测不是一回事。

- [数正常 Zeeman 谱线各偏振分量的光子](https://sandboxphysics.com/zh/labs/zeeman-polarization-spectrometer/)
- [看能级和跃迁强度怎样随磁场变化](https://sandboxphysics.com/zh/labs/coupled-spin-spectroscopy/)

## 来源与阅读说明

本文链接 1897 年的 Nature 报告和马里兰大学的扫描件，正文写到了谱线展宽和 Lorentz 对偏振的预言。Zeeman 1903 年 5 月的诺奖演讲有大学托管的可读版本，他在演讲中回顾比较了钠线展宽和镉三重线。现代弱场公式取自 NIST。本文没有重新分析任何历史底片。

1. [P. Zeeman (1897), The Effect of Magnetisation on the Nature of Light Emitted by a Substance, Nature 55, 347](https://www.nature.com/articles/055347a0)
2. [P. Zeeman (1897), original Nature report — University of Maryland scan](https://physics.umd.edu/grt/taj/623e/Zeeman1897.pdf)
3. [NIST Atomic Spectroscopy, Zeeman Effect — weak-field energy shifts and magnetic factors](https://www.nist.gov/pml/atomic-spectroscopy-compendium-basic-ideas-notation-data-and-formulas/atomic-spectroscopy-zeeman)
4. [Nobel Prize in Physics 1902 — official award record](https://www.nobelprize.org/prizes/physics/1902/summary/)
5. [P. Zeeman (1903), Light Radiation in a Magnetic Field — Nobel lecture, University of Maryland copy](https://physics.umd.edu/grt/taj/623f/Pieter%20Zeeman%20-%20Nobel%20Lecture-%20Light%20Radiation%20in%20a%20Magnetic%20Field.pdf)

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