Sunspot Magnetic Fields Observed with a Large-Format Infrared Array

Spectro-polarimetric observations of sunspots were carried out by using a PtSi near-infrared camera (KONIC) of Kiso Observatory, The University of Tokyo, in the period of 1999 November 3-5. The camera was attached to a spectrograph of the Domeless Solar Telescope at Hida Observatory, Kyoto University. We observed the absorption lines of FeI at 15648.5Å (Lande factor g_L = 1.53) and 15652.9Å (g_{L eff} = 3), and derived the distribution of the magnetic field strengths and inclination angles across the sunspots. The ratio of the Zeeman splitting of the two lines was derived to be 0.39 +/- 0.01, while the ratio of the Lande factors is 0.51. Our data indicates that the effective Lande factor of the 15652.9Å line is 1.17 +/- 0.03..