Photon echo

Japanese: フォトンエコー（英語表記）photon echo

A spectroscopic phenomenon that has a perfect analogy with spin echo in magnetic resonance. In other words, it is a phenomenon in which when an electromagnetic pulse that is almost resonant with two energy levels of a substance is irradiated with a certain time interval ( T ), light is emitted from the substance after another T time. In the case of spin echo, the movement of the magnetic moment M in the magnetic field H is described by the Bloch equation (γ is the magnetic angular momentum ratio). On the other hand, the electromagnetic wave E cosω t ( E is the electric field strength, ω is the angular frequency) that is almost resonant with the transition between two energy levels W ₁ and W ₂ is

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

磁気共鳴におけるスピンエコーとの間に完全なアナロジーが成立する分光学的現象。すなわち，物質の二つのエネルギー準位にほぼ共鳴する電磁波パルスを，ある時間間隔(T)をおいて照射したとき，さらにT時間後に物質から光の放射が起こる現象をいう。スピンエコーの場合，磁場Hの中での磁気モーメントMの運動は，ブロッホ方程式，で記述される(γは磁気角運動量比)。一方，二つのエネルギー準位W₁,W₂の間の遷移にほぼ共鳴している電磁波Ecosωt(Eは電場の強さ，ωは角振動数。

出典　株式会社平凡社世界大百科事典第２版について　情報

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