### Author Topic: Euler angles in orientation.m  (Read 2069 times)

#### johncprice

• Member
• • Posts: 2 ##### Euler angles in orientation.m
« on: September 25, 2016, 01:24:12 AM »
I have a question about Euler angles in Spinach.

I created a set of spin coordinates, rotated them using Euler angles (alpha,beta,gamma), and then created the full dipole Hamiltonian using

spin_system=assume(spin_system,'nmr');
[H,Q]=hamiltonian(spin_system,'comm');
H1=H+orientation(Q,[0,0,0]);

Now I do the same thing another way, by creating a spin system using the un-rotated coordinates and passing the Euler angles to orientation.m as follows:

spin_system=assume(spin_system,'nmr');
[H,Q]=hamiltonian(spin_system,'comm');
H2=H+orientation(Q,[gamma,-beta,alpha]);

It works! The two Hamiltonians are the same to high precision for various values of the angles.

But the call to orientation(Q,[gamma,-beta,alpha]) suggests to me that I am using the wrong Euler angle convention.  I am using the one given in Kuprov's lecture sd_m2_lecture_03.pdf which corresponds to gamma rotation about z, beta rotation about y, alpha rotation about z. Is a different one being used?

#### kuprov

• Member
•     • Posts: 58 ##### Re: Euler angles in orientation.m
« Reply #1 on: September 25, 2016, 09:47:38 AM »
Investigating...

The most likely answer is that the lectures are wrong -- rotations in Spinach kernel are extensively tested against a dozen different calculation types.

#### kuprov

•      