ConstantID

Molybdenum x unit

UnitsMeasured

xu(Mo Kα1) = 1.002 099 52(53) × 10−13 m

Value
1.002 099 52 × 10−13 m
Standard uncertainty
5.3 × 10−20 m
Relative uncertainty
5.3 × 10−7 (529 parts per billion)
Status
Measured
Symbol
xu(Mo Kα1)
Source
CODATA 2022 via NIST · NIST entry

Use in a calculation

# Molybdenum x unit, CODATA 2022 (NIST)
molybdenum_x_unit = 1.00209952e-13  # m, standard uncertainty 5.3e-20

# SciPy: scipy.constants.physical_constants['Molybdenum x unit']

What it is

An X-ray unit of length, about 10⁻¹³ m, defined so that the wavelength of the molybdenum Kα₁ line is exactly 707.831 xu(Mo Kα₁).

In other units

UnitValue
CGS (cm)1.002 099 52 × 10−11
pm picometre0.100 209 952
fm femtometre100.209 952
Å ångström0.001 002 099 52
a₀ bohr (atomic unit)0.001 893 693 64unit is itself measured

Converted with ConstantID's unit table; digits are rounded to the precision of the value, and a long exact value is rounded only for display. The relative uncertainty is unchanged by conversion to an exactly defined unit.

How the value changed, 1998–2022

Each point is one CODATA adjustment, plotted as its difference from the 2022 value; the bars show one standard uncertainty (an arrowhead means the bar runs off the chart).

Molybdenum x unit: CODATA values 1998–2022 relative to the 2022 value, in parts per billion, with one-standard-uncertainty bars−1500−1000−5000+500+1000+1500parts per billion1998200220062010201420182022

Relative uncertainty

Molybdenum x unit: relative standard uncertainty in each CODATA adjustment, logarithmic scale10⁻⁸10⁻⁷10⁻⁶1998200220062010201420182022
CODATAValue (uncertainty)Relative uncertaintyChange from previous
20221.002 099 52(53) × 10−135.3 × 10−7 +0.0 σ of 2018
20181.002 099 52(53) × 10−135.3 × 10−7 +0.0 σ of 2014
20141.002 099 52(53) × 10−135.3 × 10−7 +0.0 σ of 2010
20101.002 099 52(53) × 10−135.3 × 10−7 −0.1 σ of 2006
20061.002 099 55(53) × 10−135.3 × 10−7 −0.2 σ of 2002
20021.002 099 66(53) × 10−135.3 × 10−7 +0.1 σ of 1998
19981.002 099 59(53) × 10−135.3 × 10−7

“Change from previous” is the shift in the value divided by the standard uncertainty of the previous adjustment. Earlier values are converted into the current unit where NIST changed it (for example J s to J Hz⁻¹).