L4 - density matrix

Question 1

rho 12 meaning

Answer 1

Complex electron dispacement vector

Question 2

rho 11 or rho22

Answer 2

Population of state

Question 3

Elastic collision effectrs

Answer 3

No effect on rho11 rho22

Question 4

Average collisional rate (elastic collitions)

Answer 4

Tau
Average collisional time 1/Tau

Question 5

dRho21/dt

Answer 5

2 contril
rho. _elastic + Rho._schordinger

Question 6

Gamma_1 or 2

Answer 6

Inelastic collisional rates
DO change population

Question 7

A21

Answer 7

Einstein A coefficient
Spontaeous emission rate from 2 to 1

Question 8

If ONLY inelastic collisions, how would population fo state 1 and 2 look

Answer 8

Rho11 and 22 would have exp decay wiht rate Gamma 1 or 2

So ALL rhos die off exponentially as energy is lost due to only inelastic collisions

Question 9

Difference between eastic and inelastic

Answer 9

Elastic affects rho12 rho21 values, does NOT affect state population rho 11 and rho 22
Inelastic affects population of states rho11 and rho 22

Question 10

Beta

Answer 10

Total relaxation rate
The ‘soft’ elastic collision rate dominates
Beta = 1/Tau + 1/2(Gamma1 + Gamma2 + A21)
where 1/Tau dominates