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tokens: 2019 ). Here, the uncertainty in the wavelength calibration in Doppler units is expected to be about 1 km s −1 . Information of the two target lines and their associated calibration lines is listed in Table 2 . After the wavelength calibrations, the Si iv and Mg ii k lines have redshifts of 2.3 km s −1 and 3.1 km s −1 , respectively, in the quiet Sun region. Here, the Doppler shift of Mg ii k line is obtained using the central absorption at k3, and unrelated to the spectroscopic results of coronal rain. Figure 4. Spectral information of the coronal rain observed by IRIS. Maps of intensity (a1)–(a2), Doppler shift (b1)–(b2), and line width (c1)–(c2) of Si iv (1394 Å) (a1)–(c1) and Mg ii k (2796 Å) (a2)–(c2) lines for the IRIS raster scan #3. Like in Figure 2 (a), the blue rectangles and diamond separately indicate the positions of northern and southern parts of the coronal rain, which is enclosed by the blue dashed–dotted lines. The FOV is denoted by the pink rectangle in Figure 2 (a). See Section 4.1 for details. Table 2 Lines of Interest Note. Listed are the lines, the rest wavelengths of the lines, the Doppler shifts (Δ v ) of the rest wavelengths of the lines to the Si iv (upper) and Mg ii k (lower) lines, and the absolute Doppler shifts of the lines in the spectrum averaged over a quiet Sun region after the wavelength calibrations. Positive (negative) values of the Doppler shifts correspond to redshifts (blueshifts). The rest wavelengths of the lines are obtained from the line list of Tian ( 2017 ). Similar spectroscopic results of coronal rain are obtained for the four middle raster scans of IRIS, i.e., from scans number two to five. Among them we take the results for the third raster scan for example, and display them in Figure 4 . The left and right columns of Figure 4 show the maps of intensity, Doppler shift, and line width of the Si iv and Mg ii k lines, respectively. Here, the instrumental line width of about 26 mÅ is subtracted from the Gaussian line width (De Pontieu et al. 2014 ). In these maps, the line fit parameters outside the locations of the coronal rain are not shown as they are not well-fitted because of low count rates. Therefore, we only concentrate on the coronal rain region enclosed by the blue dashed–dotted lines in Figure 4 . Same as in the IRIS 1400 Å SJIs (see Figure 2 (a)), two substructures of the coronal rain are identified, marked separately by the blue square and diamond signs in Figure 4 . This demonstrates that in our observations in the coronal rain, the 1400 Å channel is indeed dominated by the transition region Si iv line. Comparing the Si iv and Mg ii k intensity maps, we find that the coronal rain seen in the Mg ii k line is located mostly at the same locations as the Si iv coronal rain; see Figures 4 (a1)–(a2). At the north (south) coronal rain, we measure the intensity, Doppler shift, and line width, and obtain the mean values of 46 (18) DN pixel −1 , 7.5 (5) km s −1 , and 8.6 (7.3) km s −1 for the