The effect of pressure on the nuclear quadrupole resonance and ruby fluorescence in a NiCrAl pressure cell

A pressure of 4.0 GPa was achieved using a piston-cylinder-type NiCrAl pressure cell which possesses a large sample space of 4.4 mm diameter × 15 mm length at ambient pressure. As monitors of the pressure, the ⁶³Cu nuclear quadrupole resonance (NQR) of Cu₂O and ruby fluorescence were studied at the same time. The relation between the NQR frequency and the R1 line of the ruby fluorescence was investigated at pressures below 3.2 GPa.