Near-threshold vibrational excitation of acetylene by positron impact

Journal Article · Fri Jan 15 00:00:00 EST 2010 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.81.012712· OSTI ID:21388737

Oliveira, Eliane M. de; Lima, Marco A. P.; Sanchez, Sergio d'A; Varella, Marcio T. do N. ^[1]

---

1. Instituto de Fisica Gleb Wataghin, Universidade Estadual de Campinas, 13083-970 Campinas, Sao Paulo (Brazil)

We report vibrational excitation cross sections for C-C and C-H symmetric stretch modes of acetylene by positron impact. The contribution of these infrared inactive modes to the annihilation parameter is also addressed. The Feshbach projection operator approach was employed to vibrationally resolve e{sup +}-acetylene scattering phase shifts obtained with the Schwinger multichannel method. The present results point out a virtual state pole at the equilibrium geometry of acetylene that becomes a bound state as either bond is stretched, in qualitative agreement with previous calculations for small hydrocarbons. The vibrational couplings are stronger for the C-C mode, giving rise to a bound state pole within the Franck-Condon region of the vibrational ground state. These bound and virtual states give rise to sharp threshold structures (vibrational resonances) in both the vibrational excitation cross sections and the annihilation parameter (Z{sub eff}). We found fair agreement between the present calculations and previously reported e{sup +}-acetylene vibrational excitation cross sections.

• OSTI ID: 21388737
• Journal Information: Physical Review. A, Vol. 81, Issue 1; Other Information: DOI: 10.1103/PhysRevA.81.012712; (c) 2010 The American Physical Society; ISSN 1050-2947
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ACETYLENE
ANNIHILATION
BOUND STATE
COUPLINGS
CROSS SECTIONS
EQUILIBRIUM
EXCITATION
GEOMETRY
GROUND STATES
PHASE SHIFT
POSITRONS
PROJECTION OPERATORS
RESONANCE
SCATTERING
SYMMETRY
VIRTUAL STATES
ALKYNES
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
ELEMENTARY PARTICLES
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
FERMIONS
HYDROCARBONS
INTERACTIONS
LEPTONS
MATHEMATICAL OPERATORS
MATHEMATICS
MATTER
ORGANIC COMPOUNDS
PARTICLE INTERACTIONS