Just a small question regarding collisions. Imagine a head-on collision between a photon and a particle with mass that moves with a non-relativistic speed, the particle was on its ground state, completely absorbs the photon, and moves to its next energy level. Is it always the case that the particle ends up with a non-relativistic speed after the collision?
Something more specific:
To study the properties of isolated atoms with a high degree of precision they must be kept almost at rest for a length of time. A method has recently been developed to do this. It is called “laser cooling” and is illustrated by the problem below. In a vacuum chamber a well collimated beam of Na23 atoms (coming from the evaporation of a sample at 103 K) is illuminated head-on with a high intensity laser beam (fig. 3.1). The frequency of laser is chosen so there will be resonant absorption of a photon by those atoms whose velocity is v0. When the light is absorbed, these atoms are exited to the first energy level, which has a mean value E above the ground state and uncertainty of (gamma). Find the laser frequency needed ensure the resonant absorption of the light by those atoms whose kinetic energy of the atoms inside the region behind the collimator. Also find the reduction in the velocity of these atoms, ∆v1, after the absorption process. Data E = 3,36⋅10-19 J Γ = 7,0⋅10-27 J c = 3⋅108 ms-1 mp = 1,67⋅10-27 kg h = 6,62⋅10-34 Js k = 1,38⋅10-23 JK-1