The present invention relates to a long pulse gas laser apparatus for lithography
further improved in the laser oscillation efficiency and stability increased by
addition of xenon gas. A gas laser apparatus for lithography has a pair of discharge
electrodes 2 provided in a laser chamber 1 and emits laser beam having
a laser pulse width (Tis) of not less than 40 ns by exciting a laser
gas sealed in the laser chamber 1 by electric discharge between the pair
of discharge electrodes 2, the laser gas containing xenon in an amount not
less than 2 ppm and not more than 100 ppm in partial pressure ratio. The laser
gas has been heated at least when the laser beam is emitted.
