# Thread: Forming derivative from an easy equation

1. Hi everyone,

I am currently reading a text book on quantum mechanics by Melvin Hanna. I have a fairly simply question, regarding one of the mathematical derivations. Seems I can't grasp the steps involved, despite this being a simple task.

Basically this is a step involved in transforming the Hamiltonian into atomic units from cgs units.

We set

which essentially just expresses the position in space in terms of atomic units by multiplication with the Bohr radius.

It then follows that

I would be grateful is someone could provide me with the steps involved, and direct me in the right direction to read up on this in some maths books.
This protocol of generating a differential expression from an equation appears quite frequently in QM, something that I never fully understood. Should be very simple. What keyword/term would I need to look for.

Thanks for your help

Tobias

2. Originally Posted by Tobias Kraemer
Hi everyone,

I am currently reading a text book on quantum mechanics by Melvin Hanna. I have a fairly simply question, regarding one of the mathematical derivations. Seems I can't grasp the steps involved, despite this being a simple task.

Basically this is a step involved in transforming the Hamiltonian into atomic units from cgs units.

We set

which essentially just expresses the position in space in terms of atomic units by multiplication with the Bohr radius.

It then follows that

I would be grateful is someone could provide me with the steps involved, and direct me in the right direction to read up on this in some maths books.
This protocol of generating a differential expression from an equation appears quite frequently in QM, something that I never fully understood. Should be very simple. What keyword/term would I need to look for.

Thanks for your help

Tobias
Hint:

3. Dear Andrew,

thanks for pointing me in the right direction and refreshing my mind on this. I was thinking along these lines. Easy....

Tobi

4. Originally Posted by Tobias Kraemer
Dear Andrew,

thanks for pointing me in the right direction and refreshing my mind on this. I was thinking along these lines. Easy....

Tobi
You are welcome

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