If you like the ChemWiki, please "like" us on facebook, "share" us on Google+, or "tweet" about the project.

ChemWiki: The Dynamic Chemistry E-textbook > Physical Chemistry > Quantum Mechanics > Bra-Ket Notation > Eigenvalues and eigenvectors

In general, the ket is not a constant multiple of . However, there are some special kets known as the eigenkets of operator . These are denoted

(42) |

and have the property

(43) |

where , , are numbers called eigenvalues. Clearly, applying to one of its eigenkets yields the same eigenket multiplied by the associated eigenvalue.

Consider the eigenkets and eigenvalues of a Hermitian operator . These are denoted

(44) |

where is the eigenket associated with the eigenvalue . Three important results are readily deduced:

(i) The eigenvalues are all real numbers, and the eigenkets corresponding to different eigenvalues are orthogonal. Since is Hermitian, the dual equation to Eq. (44) (for the eigenvalue ) reads

(45) |

If we left-multiply Eq. (44) by , right-multiply the above equation by , and take the difference, we obtain

(46) |

Suppose that the eigenvalues and are the same. It follows from the above that

(47) |

where we have used the fact that is not the null ket. This proves that the eigenvalues are real numbers. Suppose that the eigenvalues and are different. It follows that

(48) |

which demonstrates that eigenkets corresponding to different eigenvalues are orthogonal.

(ii) The eigenvalues associated with eigenkets are the same as the eigenvalues associated with eigenbras. An eigenbra of corresponding to an eigenvalue is defined

(49) |

(iii) The dual of any eigenket is an eigenbra belonging to the same eigenvalue, and conversely.

**Analytical Chemistry**

**Biological Chemistry**

**Inorganic Chemistry**

**Organic Chemistry**

**Physical Chemistry**

**Theoretical Chemistry**

**Cal Poly Pomona**

**Diablo Valley College**

**Florida State U**

**Hope College**

**Howard University**

**Purdue**

**Sacramento City College**

**UC Davis**

**UC Irvine**

**Zumdahl 9 ^{ed}**

An NSF funded Project

- © Copyright 2014 Chemwiki

UC Davis ChemWiki is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License. Permissions beyond the scope of this license may be available at copyright@ucdavis.edu. Questions and concerns can be directed toward Prof. Delmar Larsen (dlarsen@ucdavis.edu), Founder and Director. Terms of Use

By STEMWiki Hyperlibrary