l1={4.96405, 0.29997, 0.39996, 0.49996, 0.59996, 0.69996, 0.79997, \
0.89995, 0.99996, 1.09997, 1.19997, 1.29998, 1.39995, 1.49998, \
1.59995, 1.69995, 1.79997, 1.89997, 1.99997, 2.09998, 2.19997, \
2.29997, 2.39997, 2.49997, 2.59996, 2.69997, 2.79996, 2.89996, \
2.99996, 3.09996, 3.19995, 3.29996, 3.39996, 3.49997, 3.59998, \
3.69995, 3.79996, 3.89996, 3.99995, 4.09995, 4.19998, 4.29998, \
4.39998, 4.49998, 4.59995, 4.69998, 4.79995, 4.89998, 4.99997, \
5.09997, 5.19998, 5.29997, 5.39996, 5.49998, 5.59996, 5.69997, \
5.79997, 5.89997, 5.99997, 6.09998, 6.19996, 6.29995, 6.39998, \
6.49995, 6.59995, 6.69998, 6.79995}
l2={-6.90772, 0.00368, 0.0075, 0.01137, 0.01536, 0.01945, 0.0237, \
0.03269, 0.042, 0.05115, 0.06004, 0.06432, 0.06843, 0.0723, 0.07599, \
0.07943, 0.0826, 0.08556, 0.08833, 0.09091, 0.09328, 0.09536, \
0.09738, 0.09913, 0.10083, 0.1023, 0.10367, 0.10492, 0.10603, \
0.10707, 0.108, 0.10889, 0.10966, 0.11039, 0.11102, 0.11165, 0.1122, \
0.11269, 0.11322, 0.11366, 0.11397, 0.11429, 0.11474, 0.11497, \
0.11478, 0.11563, 0.11575, 0.11597, 0.11615, 0.11633, 0.11652, \
0.11674, 0.11687, 0.11699, 0.11712, 0.11725, 0.11737, 0.11747, \
0.11756, 0.11768, 0.11769, 0.1178, 0.11786, 0.11792, 0.118, 0.11808, \
0.11812}
l3 = Transpose[{l1, l2}]
ListPlot[l3, PlotStyle -> {PointSize[Large]}, Joined -> True,
Mesh -> All]
我想对上图中的曲线进行非线性拟合，拟合的方程如下
nu = 6.02*10^23*9.274*10^-24
ukt = (9.274*10^-24)/(1.3807*10^-23 *2)
kt = 1.3807*10^-23*2
fit = NonlinearModelFit[Most[l3],
nu*g*j*(2*j + 1)/(2*j) Cosh[(2*j + 1)/(2 j)*ukt*g*j*x] -
1/(2 j)*Cosh[(g*9.274*10^-24*j*x)/(kt*(2*j))], {g, j}, x]
所需要求解的参数为g和j
但是拟合出来的曲线一直不正确，请问该怎么设置才能得到正确的g和j
