Patent ID: 7002299

Claim:
Discharge lamp, comprising: a silica glass discharge vessel having a discharge space, and a pair of opposed electrodes located in the discharge vessel, wherein the discharge vessel contains at least 0.15 mg/mm 3 of mercury and a rare gas having argon as a main component, and bromine in an amount in a range of 2×10 −4 μmole/mm 3 to 7×10 −3 μmole/mm 3 , wherein amounts of oxygen, hydrogen and carbon which are present in the discharge space of the discharge vessel have been set so as to meet the following conditions (1) to (4) when a direct current of 5 mA is fed between the above described electrodes and a glow discharge produced: 1.0×10 −4 ≦b/a ≦1.2×10 −1 Condition (1) c/a ≦1.4×10 −1 Condition (2) d/a ≦1.2×10 −2 Condition (3) e/a ≦1.4×10 −2 Condition (4) where a is the emission intensity of the argon with a wavelength of 668 nm, b is the emission intensity of OH with a wavelength of 309 nm, c is the emission intensity of hydrogen (H) with a wavelength of 656 nm, d is the emission intensity of C 2 with a wavelength of 517 nm, and e is the emission intensity of the CH with a wavelength of 431 nm.