A student investigates the reversible decomposition of phosgene gas, \(\text{COCl}_2\text{(g)}\), in a sealed, rigid \(1.0 \text{ L}\) flask according to the following equation: \(\text{COCl}_2\text{(g)} \rightleftharpoons \text{CO(g)} + \text{Cl}_2\text{(g)}\) with \(\Delta H^\circ = +108 \text{ kJ/mol}_{rxn}\). The system is allowed to reach equilibrium at \(500 \text{ K}\). Which modification to the experimental procedure will increase the equilibrium yield of \(\text{Cl}_2\text{(g)}\)?