The actual market situation of green laser pointer should be taken intothe account

This cooling is known as the Doppler cooling, the cooling force is called the dissipative force or spontaneous radiation. Absorption and emission times per second, this retarding force is great, For 589nm the resonance light in sodium atoms, the slowing effect is equivalent to 100,000 times the acceleration due to gravity [2] atoms along the x-axis for a dimensional random movement, speed, big and small, both positive and negative direction of the relative two beams of negative detuning of the laser radiation, the atoms preferentially absorb head to the laser photons, thereby reducing the speed of cooling. Figure 1 shows the forces on atoms in this case, the visible direction of the force is always the direction and speed, and thus the damping force of the velocity tends to zero. It is during any period which can be specified by the manufacturer itself as per real situations of  green laser pointer .
Thesis of East China Institute of single-atom laser cooling in Figure 1 Doppler cooling mechanisms: (a) an atomic movement along the two beams of negative detuning is δ-shot laser standing wave field; (b) the low laser intensity, Laser negative detuning, the atoms feel the average force from the opposite direction, this static friction can be cooled atomic friction slope equal to the coefficient of friction when the velocity is zero. One-dimensional extended to three-dimensional, from the up and down before and after the six laser beams fired at atoms, what happens? To this end, in 1985 in the Bell Laboratory Steven Chu group an experiment (see Figure 2). Measured the temperature of the six-beam laser the Interchange cooling down sodium atoms, the result is 240? K,. The real situation of the unit and personnel of  green laser pointer should be considered.
In fact the atomic temperature is not capable of cooling to zero. Atomic absorption of the photon after the loss of momentum will be emitted photons to be a random recoil momentum. The emission of photons can also be close to the atomic absorption make it a random momentum. Negative detuning δ (= ν 0? Ν is) equal to the atomic resonance line width at half maximum kTmin = hΓ / 2, Γ the natural width of spectral lines. The minimum cooling temperature Tmin called Doppler cooling limit. Used for the experiments, 23 Na, 87Rb, 133Cs and NE atoms, Tmin, respectively, 240,144,125 and 23? K,. The experimental results of laser cooling in 1986, so that people doubt the temperature limit of Doppler cooling mechanism. The sales plan of  green laser pointer is based on the historical sales records.
People to rethink the correctness of the theory of Doppler cooling limit. They are almost the same time recognize that this theory is too simple, it is only based on atomic two levels (one ground state and an excited state) above. Multiple sub-level atomic system, the effect of light atoms are pumped to an energy level. Optical pumping effect in the lower than the Doppler cooling mechanism plays a very important role. -3 - Thesis of East China Institute of the single-atom laser cooling in Figure 2 with orthogonal laser beam and pulse atomic beam vacuum chamber schematic (atomic beam generated by a 10ns double-data-YAG laser evaporation of a solid-state sodium flakes. liquid nitrogen cooling of the partition is an effective low-temperature pump. The data of    green laser pointer should be well analyzed by the manufacturer.