why he ne atoms in laser

from figure below you find various materials used in lasers however in visible region it is due fact (may be confirmed  from a person of chemistry background ) their emission of radiation lies in visible region.

Diagram from wikipedia

The laser process in a HeNe laser starts with collision of electrons from the electrical discharge with the helium atoms in the gas. This excites helium from the ground state to the 23S1 and 21S0 long-lived, metastable excited states. Collision of the excited helium atoms with the ground-state neon atoms results in transfer of energy to the neon atoms, exciting neon electrons into the 3s2 level. This is due to a coincidence of energy levels between the helium and neon atoms.

laser

IN He Ne laser active centres are Ne atoms but Ne gas is inert gas so is it not difficult to excite Ne atoms ? why noble gases are used in laser ?

what is the full method of population inversion and how laser action of emitted photons is continous ?