Fig. 3: Specular and off-specular neutron scattering from the ³He/⁴He mixture for three different temperatures.

Q_z is the out-of-plane wavevector transfer and Q_x is the in-plane wavevector transfer. The intensity colour scale is logarithmic and shows the I/I₀ reflectivity for three different temperatures: 170 mK (a), 300 mK (b) and 1500 mK (c). The high-intensity critical edge can be seen for Q_x ≈ 0, Q_z ≤ 0.01 Å⁻¹. There is a significant rise in the off-specular scattering at 300 mK and low Q_z (b). This is highlighted in the pseudo rocking curves displayed in (d), where the 170 mK, 1500 mK and Si-only curves have essentially the same width, but the 300 mK curve is noticeably broader. These pseudo rocking curves were created by integrating constant lines in the Q_z direction over the Q_z range 0.01–0.03 Å⁻¹ as shown by the yellow-dashed box in (a) and are intended to highlight the changes in the reciprocal space maps rather than provide a quantitative analysis. The dead zone on the left of each image is due to the masking of several dead detector pixels in the time of flight maps when converted to reciprocal space maps. This appears as an averaged-out dip in the pseudo-rocking curves.