Question

An atom of massis initially at rest, in its ground state. Amoving(nonrelativistic) electron of mass $m_e$ collides with theatom. The atom+electron system canexist in an excited state in which the electron is absorbed intothe atom. The excited state has an extra, "internal,"energyrelative to the atom's ground state.(Intro1figure) $MLM_er_1.jpg$
A)Find the kinetic energy $K_e$ that the electron must have inorder to excite theatom.Express your answer in terms of, $m_e$ , and .

We can use the result from Part A to study a process of interestin atomic physics: a collision of two atoms that causes one of theatoms to ionize (lose anelectron). In this case, is the energy needed to ionize one ofthe atoms,called the ionization energy. The most efficient way toionize an atom in a collision with another atom is for thecollision to be completelyinelastic (atoms stick together afterthe collision). If the collision were perfectly elastic, thentranslational kinetic energy would be conserved, and therewould beno energy left over for exciting the atom. If the collision werepartially elastic, then some of the initial kinetic energy would beconverted intointernal energy, but not as much as in a perfectlyinelastic collision. In practice, interatomic collisions are neverperfectly inelastic, but analyzing thiscase can give a lower boundon the amount of kinetic energy needed for ionization.

Is it possible to ionize an atom of , initially at rest, by a collision with an atom of that has kinetic energy $K_initial$ of 4.0 electron volts? The ionization energy of thecesium atom is 3.9 electronvolts.

You can take the mass of the oxygen atom to be 16 atomic massunits and that of the cesium atom to be 133 atomic mass units. Itdoesn't matter what mass unitsyou choose, as long as you areconsistent. For this question, it is most convenient to use atomicmass units, since these are the numbers you are provided with.

	yes no
Correct

Part CWhat is the least possible initial kineticenergy $K_min$ theoxygen atom could have and still excite the cesiumatom?Express your answer in electronvolts, to one decimal place.

Answer 1

Using conservation of momentum, uf IS Using formula for kinetic energy, find K_f of the atom/atom is h-1/2(me + M)u, subbing in v_f gives me +M Using formula for kinetic energy, eliminated v_i from previous step Finally, subbing back into K_eE+K_f, I get: me The +M

Answer 2

Using conservation of momentum, uf IS Using formula for kinetic energy, find K_f of the atom/atom is h-1/2(me + M)u, subbing in v_f gives me +M Using formula for kinetic energy, eliminated v_i from previous step Finally, subbing back into K_eE+K_f, I get: me The +M

Answer 3

KE= 1/mV^2 must exceed E to have in excited state,

Answer 4