Virtual state

For the metastable state of a certain class of Feshbach resonance, see Feshbach_resonance § Unstable_State.

In quantum physics, a virtual state is a very short-lived, unobservable quantum state.[1]

In many quantum processes a virtual state is an intermediate state, sometimes described as "imaginary"[2] in a multi-step process that mediates otherwise forbidden transitions. Since virtual states are not eigenfunctions of anything,[3] normal parameters such as occupation, energy and lifetime need to be qualified. No measurement of a system will show one to be occupied,[4] but they still have lifetimes derived from uncertainty relations.[5][6] While each virtual state has an associated energy, no direct measurement of its energy is possible[7] but various approaches have been used to make some measurements (for example see [8] and related work [9][10] on virtual state spectroscopy) or extract other parameters using measurement techniques that depend upon the virtual state's lifetime.[11] The concept is quite general and can be used to predict and describe experimental results in many areas including Raman spectroscopy,[12] non-linear optics generally,[13] various types of photochemistry,[14] and/or nuclear processes.[15]

See also

References

  1. A glossary of terms in nuclear science and technology: a series of nine sections By National Research Council (U.S.). Conference on Glossary of Terms in Nuclear S American Society of Mechanical Engineers, 1953 page 61
  2. Science, Volume 227 American Association for the Advancement of Science, HighWire Press, JSTOR 1985 page 736
  3. Barry R. Masters, Peter T. C. So Handbook of Biomedical Nonlinear Optical Microscopy Oxford University Press US, 2008 ISBN 0-19-516260-9 ISBN 978-0-19-516260-8 page 10
  4. David Alan Wardle Raman Scattering in Optical Fibres, thesis Doctor of Philosophy in Physics The University of Auckland, January 1999 page 22
  5. Nonlinear Optics and Laser Spectroscopy By S C Abbi, S. A. Ahmad page 139 ISBN 81-7319-354-1, ISBN 978-81-7319-354-5
  6. Non-linear optical properties of matter: from molecules to condensed phases By Manthos G. Papadopoulos, Andrzej Jerzy Sadlej, Jerzy Leszczynski page 3 Springer, 2006 ISBN 1-4020-4849-1, ISBN 978-1-4020-4849-4
  7. Dzevad Belkic Principles of quantum scattering theory page 70 CRC Press, 2004 ISBN 0-7503-0496-0, ISBN 978-0-7503-0496-2
  8. Bahaa E. A. Saleh, Bradley M. Jost, Hong-Bing Fei, and Malvin C. Teich Entangled-Photon Virtual-State Spectroscopy VOLUME 80, NUMBER 16 PHY S I CAL REV I EW LETTERS 20 APRIL 1998 S0031-9007(98)05928-6 page 3483
  9. Jun KojimaCorresponding Author Contact Information, a, E-mail The Corresponding Author and Quang-Viet Nguyen Entangled biphoton virtual-state spectroscopy of the A2Σ+–X2Π system of OH Chemical Physics Letters Volume 396, Issues 4-6, 1 October 2004, Pages 323-328
  10. Dong-Ik Lee and Theodore Goodson III Quantum spectroscopy of an organic material utilizing entangled and correlated photon pairs Proc. SPIE, Vol. 6653, 66530V (2007); doi:10.1117/12.745492
  11. F. Boitier, A. Godard, E. Rosencher & C. Fabre Measuring photon bunching at ultrashort timescale by two-photon absorption in semiconductors Nature Physics 5, 267 - 270 (2009) Published online: 15 March 2009 doi:10.1038/nphys1218
  12. Peter R. Griffiths, James A. De Haseth Fourier Transform Infrared Spectrometry, Volume 83 second ed, Wiley-Interscience, 2007 ISBN 0-470-10629-8 ISBN 978-0-470-10629-7 page 16
  13. S C Abbi, S. A. Ahmad Nonlinear Optics and Laser Spectroscopy, Alpha Science Int' Ltd., 2001 ISBN 81-7319-354-1 ISBN 978-81-7319-354-5 page 139
  14. Douglas C. Neckers, William S. Jenks, Thomas Wolff Advances in Photochemistry, Volume 29 John Wiley and Sons, 2006 ISBN 0-471-68240-3 ISBN 978-0-471-68240-0 page 116
  15. Proceedings of the NATIONAL ACADEMY OF SCIENCES Volume 67 Number 4 * April 15, 1967 VIRTUAL COULOMB EXCITATION IN NUCLEON TRANSFER* BY G. BREIT
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