Chapter 2
Quantum Mechanics – I
2.1 Basic Concepts and Formulae
Wave number
ν ̃=1
λ(2.1)
1fm= 10 −^15 m; 1A ̊ = 10 −^10 m; 1 nm = 10 −^9 m; 1μm = 10 −^6 m;c =
197 .3Mev−fm
Photon energy
E=hv (2.2)Photon momentum
p=hν/cPhoton energy−wavelength conversion
λ(nm)=1241
E(eν)(2.3)
de Broglie wavelength
λ=h/p (2.4)λ(electron) :λ(A) ̊ =(150/V)^1 /^2 (2.5)
λ(neutron) :λ(A) ̊ = 0. 286 E−^1 /^2 (Ein ev) (2.6)Atomic units
The Bohr radius^2 /mee^2 is frequently used as the unit of length in atomic physics.
In atomic units the energy is measured in multiples of the ionization energy of
hydrogen atom that ismee^4 / 2 ^2. In these units^2 =1,e^2 =2 andme =^12 in
all equations.
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