Photodoping of Effects in Underdoped Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+x}$ Revealed by Time and Angle Resolved Photoemission Spectroscopy*

While in the last several years great strides have been made in the use of ultrafast optical excitation to induce non-equilibrium effects in the superconducting state of cuprate high $T_{c}$ superconductors, less attention has been paid to what such pump-probe experiments might reveal about the equilibrium properties of these materials, particularly in their normal states. Recently we have investigated the non-equilibrium properties of the normal state of optimally doped Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+x}$ ($T_{c}$ = 91 K) using time and angle resolved photoelectron spectroscopy (tr-ARPES). This effort revealed a pump-induced modification of the nodal mass renormalization at 70 meV as well as a longer-lived photodoping effect. Building on this work, we will present further findings related to the photodoping effect as it is manifested in the normal state of underdoped ($T_{c}$ = 50 K) Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+x}$.