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Gratings

NIFS has four gratings physically mounted in the dewar which are briefly described in the tables below, the first table gives the standard grating properties. It also states the defaultconfigurations of grating choice which is used in conjunction with a dual blocking filter, one ofZ-J, J-H, or H-K for Z and J, H, and K gratings, respectively.

It is possible to tune the central wavelengths of the NIFS gratings to reach the inter-band regions where telluric absorption is worse. The limits on the central wavelength tuning range for each grating are given in the second table. Delivered central wavelengths are accurate to within 10%.

Table 1: Properties of the standard NIFS Z, J, H and K-band settings.

Grating Name Associated Filter Central Wavelength (microns) Spectral Range Spectral Resolution Velocity Resolution (km/s)
Z ZJ 1.05 0.94-1.15 4990 60.1
J ZJ 1.25 1.15-1.33 6040 49.6
H JH 1.65 1.49-1.80 5290 56.8
K HK 2.20 1.99-2.40 5290 56.7

 

Table 2: The NIFS gratings can be tuned to different central wavelengths. The short and long limits of the possible tuned central wavelengths and the associated filters required are:

Grating Name Short Wavelength Limit (microns) Long Wavelength Limit (microns) Short Wavelength Filter Long Wavelength Filter
Z 0.94 1.16 ZJ ZJ
J 1.14 1.36 ZJ JH
H 1.48 1.82 JH HK
K 1.98 2.41 HK HK