has value type list of doubles grid coordinate interpolation rustims-approximated Bruker timsTOF ion mobility grid model 2 parameters A grid model that approximates Bruker's timsTOF ion mobility calibration model 2. $x_i = 1 / (c_6 + c_7 / (a * i + b))$ and $i_x = (c_7 / (1/x - c_6) - b) / a$ where $a$ is a slope, $b$ an intercept, and $c_6$ and $c_7$ are parameters fit during data acquisition. The parameters are encoded $[c_6, c_7, b, a]$. MS:1004030 MS