DOF是什么意识啊??

Chemical shift references information (room temperature 25 C)
Proton (1H): (date:10/15/99)
Base frq (spcfrq when tof = 0):599.774469Mhz
0 ppm frq = 599.771398067 Mhz
tof = 2.20 ppm = -1753.34 hz
tof = 4.0 ppm = -673.73 hz
tof = 4.74 ppm = -229.9 hz
tof = 6.0 ppm = 525.81 hz
tof = 7.10 ppm = 1185.56 hz
tof = 7.30 ppm = 1305.50 hz

Carbon (13C): (date:10/15/99)
Base frq (spcfrq with dof = 0): 150.8261168 Mhz
0 ppm frq = 150.8125300393 Mhz
(note: calculated from gH/gC at 0 ppm)
dof = 31 ppm = -8911.57 hz
dof = 56 ppm = -5141.26 hz
dof = 58 ppm = -4839.635 hz
dof = 125.5 ppm = 5340.21 hz
dof = 170 ppm = 12051.37 hz
dof = 174 ppm = 12654.62 hz
dof = 176 ppm = 12956.24 hz

Nitrogen (15N): (date:9/10/99)
Base frq (spcfrq with dof2 = 0): 60.7797190 Mhz
0 ppm frq = 60.7743215988 Mhz
dof2 = 117 ppm = 1713.1944 hz

113Cd (date:11/8/99)
Base frq (dof =0): 133.0230461 Mhz
dof = 0 ppm = -39121.4 hz
(Based on 113Cd standard, the number above is not exact)
protein sample = 15000 hz

109Ag (date:12/16/99)
Base frq (dof=0): 27.903 Mhz
dof = 0 ppm = -1950 hz
(Based on AgNO3 standard sample)
protein sample: dof2 = 17584 hz

199Hg (date:1/25/00)
Base frq (dof = 0): 106.885 Mhz
dof = 0 ppm = 539259 hz


207Pb (date:1/27/00)
Base frq (dof = 0): 125.101 Mhz
dof = 0 ppm = -157.557 hz
(Based on a Pb standard sample)