Luminous afterglow time and its measurement

An important characteristic of luminescent materials is its luminous duration. According to the duration of luminescence, luminescence can be divided into fluorescence and phosphorescence. The gap between excitation and emission of fluorescence is very short, about < 10-* s. As soon as the light source leaves, the fluorescence will disappear. Phosphorescence will emit light for a long time after the excitation source leaves. Afterglow can also be used to indicate the duration of light emission. Afterglow is defined as: when the luminous brightness (or intensity > J when the excitation light stops decaying to 10% of Jo, the elapsed time is called afterglow time, which is called afterglow for short. According to the afterglow, luminescent materials can be divided into six ranges: extremely short afterglow ≤1us, short afterglow 1 ~ 10 us, medium and short afterglow 0.01 ~ 1 rms, medium afterglow 1 ~ 100ms, long afterglow 0.1 ~ 1s and extremely long afterglow > 1s. When the temperature of any luminescent material rises to a certain temperature, the luminous intensity will decrease significantly, which is the so-called thermal quenching effect. In Figure 4-17, the potential energy curves of the ground state and the excited state intersect at point E.. At this point, the excited ions can return to the ground state (e is also a point on the potential energy curve of the ground state) without changing the energy, and then vibrate back to the low energy level of the ground state through a series of changes. Therefore, the “thermal quenching” effect of E-point luminescence represents a spillorer point. If the ion in the excited state can get enough vibration energy to reach point E, it will overflow the vibration energy level of the ground state. If so, all the energy is released in the form of vibration energy, so no light is generated. Obviously, the energy at point E is critical. Generally speaking, when the temperature rises, the ion heat energy increases, and then it enters the higher vibration energy level in turn, and it may reach the E point.

An important characteristic of luminescent materials is its luminous duration. According to the duration of luminescence, luminescence can be divided into fluorescence and phosphorescence. The gap between excitation and emission of fluorescence is very short, about < 10-* s. As soon as the light source leaves, the fluorescence will disappear. Phosphorescence will emit light for a long time after the excitation source leaves. Afterglow can also be used to indicate the duration of light emission. Afterglow is defined as: when the luminous brightness (or intensity > J when the excitation light stops decaying to 10% of Jo, the elapsed time is called afterglow time, which is called afterglow for short. According to the afterglow, luminescent materials can be divided into six ranges: extremely short afterglow ≤1us, short afterglow 1 ~ 10 us, medium and short afterglow 0.01 ~ 1 rms, medium afterglow 1 ~ 100ms, long afterglow 0.1 ~ 1s and extremely long afterglow > 1s. When the temperature of any luminescent material rises to a certain temperature, the luminous intensity will decrease significantly, which is the so-called thermal quenching effect. In Figure 4-17, the potential energy curves of the ground state and the excited state intersect at point E.. At this point, the excited ions can return to the ground state (e is also a point on the potential energy curve of the ground state) without changing the energy, and then vibrate back to the low energy level of the ground state through a series of changes. Therefore, the “thermal quenching” effect of E-point luminescence represents a spillorer point. If the ion in the excited state can get enough vibration energy to reach point E, it will overflow the vibration energy level of the ground state. If so, all the energy is released in the form of vibration energy, so no light is generated. Obviously, the energy at point E is critical. Generally speaking, when the temperature rises, the ion heat energy increases, and then it enters the higher vibration energy level in turn, and it may reach the E point.