NIST Physical constant (2018)
cgs Units

Clear["Global`*"];rule1={me->9.109383701528 (10^(-28)),qe->4.8032042510 (10^(-10)),ge->2.00231930436256,kB->1.380649 (10^(-16)), c->2.99792458 (10^10),  α->7.2973525693 (10^(-3)),u->1.66053906660 (10^(-24)),mp->1.67262192369 (10^(-24)),mn->1.6749274980495 (10^(-24)),  rB->5.29177210903 (10^(-9)), μB->9.274010078328 (10^(-21)),μN->5.0507837461 (10^(-24)),   h->6.62607015 (10^(-27)), ℏ->1.054571817 (10^(-27)),λc->2.42631023867 (10^(-10)),eV->1.602176634 (10^(-12)),MeV->1.602176634 (10^(-6)),Ry->13.605693122994 eV, σSB->5.670374419 (10^(-5)), z0->376.73031366857, Φ0->2.067833848 (10^(-7)), Mea->5.9736 (10^27), Rea->6.3781   (10^8) , Msun->1.98847 (10^33), Rsun->6.9570 (10^10),Mmoon->7.3483 (10^28), ly->9.4607 (10^17), pc->3.0857   (10^18), AU->1.495978707  (10^13),mile->1.609344 (10^5), hour->3600, fm->(10^(-13)), nm->(10^(-7)), Å->(10^(-8)),NA->6.02214076 (10^23),R->8.314462618 (10^7), cal->4.184 (10^7), atm->101325 , g->9.80665 (10^2),G->6.6743015  (10^(-8))};

me:		Mass of electron			(g)
qe:		Electron charge			(esu)
ge:		g-factor of electron			
kB:		Boltzmann constant		(erg/K)
c:		Speed of light in vacuum		(cm/s)
α:		Fine structure constant
u:		Atomic unit mass			(g)
mp:		Mass of proton				(g)
mn:		Mass of neutron			(g)
rB:		Bohr radius				(cm)
μB:		Bohr magneton			(erg/G=emu)	
μN:		Nuclear magneton			(erg/G=emu)	
 ℏ:		Dirac constant				(erg s)
 h:		Planck constant			(erg  s)
 λc:		Compton wavelength		(cm)	

		

		



			
Ry:		Rydberg constant			(erg)
σSB:		Stefan-Boltzmann constant	[erg/(s (cm^2)(K^4))]	
z0:		Impedance of free space		(Ω)
Φ0:		Magnetic flux quantum		(G (cm^2))
fm 		= (10^(-13)) cm
1 Å		=(10^(-8)) cm
cal:		Calorie					(erg)
atm:		Atmosphere				(dyne/(cm^2))
NA:		Avogadro’s number 		((mole^(-1)))
G:		Gravitational constant		(dyne (cm^2)/(g^2) )
g:		acceleration of gravity		(cm/(s^2))
Mmoon: 	Mass of moon 				(g)
Rsun:	Radius of sun 				(cm)
Mea:		Mass of earth				(g)
Rea:		radius of earth				(cm)
Msun:	Mass of sun				(g)
pc:		parsec					(cm)			
ly: 		light year					(cm)
AU: 		Astronomical unit			(cm)

Fine structure constant

((qe^2)/(ℏ c)) //.rule1//ScientificForm

((%)^(-1))

Bohr radius

(( (ℏ^2))/((qe^2)me Å)) //.rule1

Hydrogen atom ground state energy

-(1/2)((me (c^2) (α^2))/eV)//.rule1

Magnetic flux quantum

((2 π ℏ c)/(2 qe ))//.rule1

Bohr magneton

(( qe ℏ)/(2 me c ))//.rule1

NumberForm[%,16]

Nuclear magneton

(( qe ℏ)/(2 mp c ))//.rule1

NumberForm[%,16]

Classical electron radius

((qe^2)/(me (c^2)))//.rule1

NumberForm[%,16]

Electron mass

((me (c^2))/MeV)//.rule1

NumberForm[%,16]