forbidden transition: meaning, definition, pronunciation and examples
C1/C2 (Very Low in general English, used only in specialised technical contexts)Highly technical, academic, scientific (physics, chemistry).
Quick answer
What does “forbidden transition” mean?
In physics (especially quantum mechanics and spectroscopy), a transition between two energy levels of a quantum system that is highly improbable according to the standard selection rules, making it extremely unlikely to occur under normal conditions.
Audio
Pronunciation
Definition
Meaning and Definition
In physics (especially quantum mechanics and spectroscopy), a transition between two energy levels of a quantum system that is highly improbable according to the standard selection rules, making it extremely unlikely to occur under normal conditions.
It can be metaphorically extended to any change or movement that is considered highly improbable or strongly prohibited according to the established rules of a system, whether scientific, social, or procedural. In a looser metaphorical sense, it refers to something that is very unlikely to happen.
Dialectal Variation
British vs American Usage
Differences
No significant differences in meaning or usage. Spelling follows standard conventions (e.g., 'spectroscopy' vs no change).
Connotations
Purely technical in both varieties.
Frequency
Extremely rare in everyday language in both regions, confined to university-level physics and related research papers.
Grammar
How to Use “forbidden transition” in a Sentence
The transition from [Energy Level A] to [Energy Level B] is a forbidden transition.Scientists observed a normally forbidden transition.The selection rules forbid this transition, making it a forbidden transition.Vocabulary
Collocations
Examples
Examples of “forbidden transition” in a Sentence
verb
British English
- The selection rules forbid that specific transition.
- The symmetry of the system forbids the transition.
American English
- The selection rules forbid that particular transition.
- The system's symmetry forbids the transition.
adverb
British English
- The electron almost never transitions thusly; it is, for all practical purposes, forbiddenly.
- (Note: 'forbiddenly' is not a standard word; this illustrates its absence.)
American English
- (No standard adverbial form exists for this term.)
adjective
British English
- The forbidden-transition line was very faint in the spectrograph.
- They studied forbidden-transition probabilities.
American English
- The forbidden transition line was very faint on the spectrograph.
- They studied forbidden transition probabilities.
Usage
Meaning in Context
Business
Not used. A metaphorical extension might be: 'A direct merger between those two market leaders is considered a forbidden transition by regulators.'
Academic
Primary context. 'The paper discusses the detection of a magnetic dipole forbidden transition in the ionised calcium spectrum.'
Everyday
Virtually never used. A forced, incorrect usage would be: 'Me suddenly liking broccoli is a forbidden transition.' (Humorous, niche)
Technical
Standard usage in physics, chemistry, materials science. 'Forbidden transitions can sometimes occur due to second-order perturbations or in imperfect symmetries.'
Vocabulary
Synonyms of “forbidden transition”
Strong
Neutral
Weak
Vocabulary
Antonyms of “forbidden transition”
Watch out
Common Mistakes When Using “forbidden transition”
- Using it as a fancy synonym for 'prohibited' in non-scientific contexts, which sounds unnatural and pretentious.
- Confusing it with 'impossible transition'; forbidden transitions are improbable, not strictly impossible.
- Misspelling as 'forbiden transition'.
FAQ
Frequently Asked Questions
No. It is highly improbable under the primary 'selection rules', but it can occur through weaker, secondary mechanisms (like magnetic dipole or electric quadrupole transitions) or in systems with broken symmetry. Its probability is just many orders of magnitude lower than an 'allowed' transition.
It would sound highly technical and out of place. In everyday language, you would say 'very unlikely change', 'improbable shift', or simply 'that's not allowed'. Using the full term is for specialised or humorous/metaphorical effect among knowledgeable listeners.
In 'forbidden fruit', the prohibition is moral, legal, or authoritative (by God, society). In 'forbidden transition', the prohibition is inherent in the mathematical rules (selection rules) derived from the laws of quantum physics. It's about probability, not morality.
Yes. Common classifications include electric dipole forbidden, magnetic dipole allowed (or vice-versa), spin-forbidden (where the spin multiplicity changes), and symmetry-forbidden. Each has its own specific set of violated selection rules.
In physics (especially quantum mechanics and spectroscopy), a transition between two energy levels of a quantum system that is highly improbable according to the standard selection rules, making it extremely unlikely to occur under normal conditions.
Forbidden transition is usually highly technical, academic, scientific (physics, chemistry). in register.
Forbidden transition: in British English it is pronounced /fəˈbɪd.ən trænˈzɪʃ.ən/, and in American English it is pronounced /fərˈbɪd.ən trænˈzɪʃ.ən/. Tap the audio buttons above to hear it.
Learning
Memory Aids
Mnemonic
Imagine a sign between two stairs on a quantum energy ladder saying 'FORBIDDEN - Do Not Step'. The rules of quantum physics are the security guard.
Conceptual Metaphor
RULES ARE PHYSICAL LAWS. A forbidden transition is a 'path blocked by the laws of nature itself'.
Practice
Quiz
In which field is the term 'forbidden transition' primarily used?