parameter

defining formula

calculated value

measured value

the velocity of zero-point oscillations of helium atom

$\widehat{v_0}=c{\alpha }^3$

116.5 m/s

The density of atoms in liquid helium

$n=\sqrt{\frac{M_4}{2m_e}}\frac{{\alpha }^2}{a_B^3}$

2.172 × 10²² atom/cm³

The density of liquid helium-4 g/l

$\gamma =M_{4}n$

144.3

${145}_{T\simeq T_{\lambda }}$

The dielectric constant of liquid helium-4

$\frac{\epsilon -1}{\epsilon +2}=\frac{4\text{π}}{3}{\alpha }^2\sqrt{\frac{M_4}{2m_e}}$

1.040

${1.048}_{T\simeq 4.2}$

${1.057}_{T\simeq T_{\lambda }}$

The temperature λ-point, K

$T_{\lambda }\simeq \frac{M_4{c}^2{\alpha }^6}{3k}$

2.1778

2.1768

The boiling temperature of helium-4, K

$T_{boil}\simeq 2T_{\lambda }$

4.35

4.21

The first sound velocity, m/s

$c_{s1}=2\widehat{v_0}$

233

${238.3}_{T\to 0}$