Shielding difference of t and p in HT

$σ_{tp}$ = 2.394 50(20) × 10⁻⁸

Value: 2.394 50 × 10⁻⁸
Standard uncertainty: 2 × 10⁻¹²
Relative uncertainty: 8.4 × 10⁻⁵ (84 parts per million)
Status: Measured
Symbol: $σ_{tp}$
Source: CODATA 2022 via NIST · NIST entry

Use in a calculation

# shielding difference of t and p in HT, CODATA 2022 (NIST)
shielding_difference_of_t_and_p_in_ht = 2.3945e-8  # standard uncertainty 2e-12

# SciPy: scipy.constants.physical_constants['shielding difference of t and p in HT']

What it is

The difference between the magnetic shielding of the triton and of the proton in the HT molecule, used to obtain the triton's magnetic moment from measurements on HT.

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).

Relative uncertainty

CODATA	Value (uncertainty)	Relative uncertainty	Change from previous
2022	2.394 50(20) × 10⁻⁸	8.4 × 10⁻⁵	−9.8 σ of 2018
2018	2.4140(20) × 10⁻⁸	8.3 × 10⁻⁴

“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).