励起

• Reading: れいき
• Romaji: reiki
• Kanji breakdown: 励 (rei) — encourage, rouse, stimulate; 起 (ki) — rise, wake up, begin
• Pronunciation: /ɾeː.ki/

Meaning

Excitation; stimulation. In physics and chemistry, the process of raising an atom, molecule, or nucleus from its ground state to a higher energy state.

When a particle absorbs energy (from light, heat, or collision), it undergoes 励起 — moving from its ground state (基底状態) to an excited state (励起状態). Upon returning to the ground state, it releases energy as a photon, which is the basis for fluorescence, phosphorescence, and lasers. Central to quantum mechanics, photochemistry, spectroscopy, and materials science.

Examples

1. 原子が光子を吸収すると電子が励起され、エネルギーの高い軌道に遷移する。 When an atom absorbs a photon, its electron is excited and transitions to a higher-energy orbital.
2. レーザーは励起状態にある原子を誘導放出によって制御することで実現される。 A laser is realised by controlling atoms in an excited state through stimulated emission.
3. 蛍光物質が励起されると、吸収した光より長い波長の光を放出する現象が起きる。 When a fluorescent substance is excited, a phenomenon occurs in which it emits light of a longer wavelength than the light it absorbed.

Usage Guide

Context: physics, quantum mechanics, chemistry, laser technology

Tone: technical

Origin & History

Compound of 励 (encourage, rouse, stimulate) + 起 (rise, awaken). In physics the term captures the image of an atom being 'roused' from its resting ground state into a higher-energy excited state.

Cultural Context

Era: Modern

Generation: Adults (specialist)

Social background: Academic/Scientific