X-Ray Data Booklet

Section 5.1  PHYSICAL CONSTANTS

 

Table 5-1 was drawn from the recommendations of CODATA (the Committee on Data for Science and Technology). The full 1998 CODATA set of constants may be found at http://physics.nist.gov/cuu/Constants/index.html. A PDF version of this table is also available.

Table 5-1. Physical constants.



Quantity


Symbol, equation


Value

Uncert.
(ppb)

speed of light

c (see note *)

2.997 924 58´108 m s–1 (1010 cm s–1)

exact

Planck constant

h

6.626 068 76(52)´10–34 J s (10–27 erg s)

78

Planck constant, reduced

= h/2p

1.054 571 596(82)´10–34 J s = 6.582 118 89(26)´10–22 MeV s

78, 39

electron charge magnitude

e

4.803 204 20(19)´10–10 esu = 1.602 176 462(63)´10–19 C

39, 59

conversion constant

197.326 960 1(78) MeV fm (= eV nm)

39

electron mass

me

0.510 998 902(21) MeV/c2 = 9.109 381 88(72)´10–31 kg

40, 79

proton mass

mp

938.271 998(38) MeV/c2 = 1.672 621 58(13)´10–27 kg

40, 79

 

 

= 1.007 276 466 88(13) u = 1836.152 667 5(39) me

0.13, 2.1

deuteron mass

md

1875.612 762 (75) MeV/c2

40

unified atomic mass unit (u)

(mass 12C atom)/12 = (1 g)/(NA mol)

931.494 013(37) MeV/c2 = 1.660 538 73(13)´10–27 kg

40, 79

permittivity of free space

e0 = 1/(m0c2)

8.854 187 817¼´10–12 F m–1

exact

permeability of free space

m0

4p´10–7 N A–2 = 12.566 370 614¼´10–7 N A–2

exact

fine-structure constant

a = e2/4pe0

1/137.035 999 76(50)

3.7

classical electron radius

re = e2/4pe0mec2

2.817 940 285(31)´10–15 m

11

Bohr radius (mnucleus = ¥)

a0 = 4pe0/mee2 = rea–2

0.529 177 208 3(19)´10–10 m (10–8 cm)

3.7

Rydberg energy

hcR¥ = mee4/2(4pe0)2

=mec2a2/2

13.605 691 72(53) eV

39

Thomson cross section

sT = 8p/3

0.665 245 854(15) barn (10–28 m2)

22

Bohr magneton

mB = e/2me

5.788 381 749(43)´10–11 MeV T–1

7.3

nuclear magneton

mN = e/2mp

3.152 451 238(24)´10–14 MeV T–1

7.6

electron cyclotron freq./field

/B = e/me

1.758 820 174(71)´1011 rad s–1 T–1

40

proton cyclotron freq./field

/B = e/mp

9.578 834 08(38)´107 rad s–1 T–1

40


 

Table 5-1. Physical constants(continued).



Quantity


Symbol, equation


Value

Uncert.
(ppb)

Avogadro constant

NA

6.022 141 99(47)´1023 mol–1

79

Boltzman constant

k

1.380 650 3(24)´10–23 J K–1 = 8.617 342(15)´10–5 eV K–1

1700

molar volume, ideal gas at STP

NAk (273.15 K)/(101 325 Pa)

22.413 996(39)´10–3 m3 mol–1

1700

p = 3.141 592 653 589 793 238

e = 2.718 281 828 459 045 235

g = 0.577 215 664 901 532 861

The meter is the length of the path traveled by light in vacuum during a time interval of 1/299 792 458 of a second.

     1 in.     =     2.54 cm

1 newton    =     105 dyne

    1 eV/c2      =     1.782 662´10–33 g

1 coulomb      =       2.997 924 58´109 esu

      1 Å     =     10–8 cm

  1 joule       =     107 erg

hc/(1 eV)       =     1.239 842 mm

    1 tesla         =       104 gauss

     1 fm     =     10–13 cm

      1 cal       =     4.184 joule

     1 eV/h       =     2.417 989´1014 Hz

      1 atm         =       1.013 25´106 dyne/cm2

1 barn     =     10–24 cm2

      1 eV       =     1.602 176 5´10–12 erg

     1 eV/k      =     11 604.5 K

         0°C         =       273.15 K