Definition of atomic units

t = 2.4189 10-17s Atomic unit of time
1 hartree = 27.2113961 eV Atomic unit of energy
=219474.63068 cm-1
= 627.50956 kcal mol-1
me = 9.1093897 10-31kg Atomic unit of mass
= 5.4857990 10-4 a.m.u.

Definition non-SI units

1 cal = 4.184 J (def.) calorie
1 erg = 1 10-7 J (def.) erg
1 Å = 1 10-10m (def.) Ångström

Physical Constants

N = 6.0221367 1023 mol-1Avogadro constant
k = 1.380658 10-23J K-1Boltzmann constant
R00= 1.097373153107 m-1 Rydberg constant
h = 6.6260755 10-34J sec Planck constant
mu = 1.6605402 10-27kg Atomic Mass Constant
a0 = 0.52917724910-10m Bohr constant
c = 2.99792458 108 m s-1Speed of Light
mp = 1.6726231 10-27kg proton mass
me = 9.1093897 10-31kg electron mass
e = 1.6022 10-19C electron charge

See also: CRC Handbook of Chemistry and Physics, 72nd edition, p. 1-18.

Energy Conversion Table (analytical)

Eh eV cm-1 Hz K J J/mol
Eh 1 2R00hc/e2R00/1002R00c2R00hc/k2R00hc2R00hcN
eV e/(2R00hc) 1 e/(100hc) e/h e/k e eN
cm-1100(2R00) 100hc/e 1 100c 100hc/k 100hc 100hcN
Hz 1/(2R00c) h/e 1/(100c) 1 h/k h hN
K k/(2R00hc) k/e k/(100hc) k/h 1 k kN
J 1/(2R00hc) 1/e 1/(100hc) 1/h 1/k 1 N
J/mol 1/(2R00hcN)1/eN 1/(100hcN) 1/(hN) 1/(kN) 1/N 1

Energy Conversion Table (numerical)

Eh eV cm-1Hz K J J/mol
Eh 1 2.7211396 101 2.1947463 105 6.5796839 1015 3.1577322 105 4.3597482 10-18 2.6255000 106
eV 3.6749309 10-2 1 8.0655409 103 2.4179883 1014 1.1604448 104 1.6021773 10-19 9.6485309 104
cm-14.5563353 10-6 1.2398424 10-4 1 2.9979246 1010 1.4387687 1.9864475 10-23 1.1962658 101
Hz 1.5198299 10-16 4.1356692 10-15 3.3356410 10-11 1 4.7992157 10-11 6.6260755 10-34 3.9903132 10-10
K 3.1668297 10-6 8.6173857 10-5 6.9503877 10-1 2.0836738 1010 1 1.3806580 10-23 8.3145112
J 2.2937104 1017 6.2415064 1018 5.0341125 1022 1.5091890 1033 7.2429233 1022 1 6.0221367 1023
J/mol 3.8087983 10-7 1.0364272 10-5 8.3593461 10-2 2.5060689 109 1.2027165 10-1 1.6605402 10-24 1

Atomic masses (including electrons) of most abundant isotope in a.m.u.

1H1.007825
2D2.0140
4He4.0026
12C12
14N14.00307
16O15.99491462
19F18.9984
32S31.97207
35Cl34.96885
40Ar39.962383124
40Ca40.08

Prefixes for use in S.I. units.

amount

prefix

symbol

10-18

atto

a

10-15

femto

f

10-12

pico

p

10-9

nano

n

10-6

micro

µ

10-3

milli

m

10-2

centi

c

10-1

deci

d

101

deca

da

102

hecto

h

103

kilo

k

106

mega

M

109

giga

G

1012

tera

T

1015

peta

P

1018

exa

E


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Last update: Sat Aug 7 13:17:54 BST 2004 e-mail: