2 Observations and data reductions

The spectra were obtained at the Nordic Optical Telescope (NOT) with the SOFIN échelle spectrograph (Tuominen 1992) in 1997. The 2nd optical camera ( $R\approx 60\thinspace 000$) and the 3rd optical camera ( $R\approx 30\thinspace 000$) were used. The spectra were recorded with the Astromed-3200 CCD camera (Mackay 1986) equipped with an EEV P88100 UV-coated CCD of $1152\times298$ pixels operated at the working temperature of 150 K. With the 2nd camera we observed simultaneously 13 spectral orders, each of 40-60 Å in length, located from 5650 Å to 8130 Å and with the 3rd camera we observed 25 spectral orders, each of 80-150 Å in length, located from 4500 Å to 8750 Å. All spectra were exposed to $S/N\ge100$.

Reductions of the CCD images were made with the 3A software package (Ilyin 1996, 2000). Procedures of bias subtraction, spike elimination, flat field correction, scattered light subtraction, extraction of spectral orders were used for image processing. A Th-Ar comparison spectrum was used for the wavelength calibration. The continuum was defined by a number of narrow spectral regions, selected to be free of lines in the solar spectrum.

The lines suitable for measurement were chosen using the requirement that the profiles be sufficiently clean to provide reliable equivalent widths. Inspection of the solar spectrum (Kurucz et al. 1984) and the solar line identifications of Moore et al. (1966) were used to avoid blends. Lines blended by telluric absorption lines were omitted from treatment as well. The equivalent widths of lines were measured by fitting of a Gaussian function. The line measurements are listed in Table 1 (available in electronic form at CDS).