# Anisotropic two-body dissociation by highly charged ion impact

Jyoti Rajput, A. Agnihotri, A. Cassimi, X. Fléchard, S. Guillous, W.

Iskandar, A. Méry, J. Rangama, C.P. Safvan

► To cite this version:

Jyoti Rajput, A. Agnihotri, A. Cassimi, X. Fléchard, S. Guillous, et al., Anisotropic two-body dissociation by highly charged ion impact. 30th International Conference on Photonic, Electronic, and Atomic Collisions, Jul 2017, Cairns, Australia. pp.102003, 10.1088/1742-6596/875/11/102003. hal-01645814

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Submitted on 1 Jun 2022

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# Anisotropic two-body dissociation by highly charged ion impact

To cite this article: Jyoti Rajput et al 2017 *J. Phys.: Conf. Ser.* **875** 102003

View the [article online](#) for updates and enhancements.

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# Anisotropic two-body dissociation by highly charged ion impact

Jyoti Rajput<sup>*1*</sup>, A. Agnihotri<sup>†</sup>, A. Cassimi<sup>†</sup>, X. Fléchard<sup>‡</sup>, S. Guillous<sup>†</sup>, W. Iskandar<sup>§</sup>, A. Méry<sup>†</sup>, J. Rangama<sup>†</sup>, C. P. Safvan<sup>¶</sup>

*<sup>†</sup> Department of Physics and Astrophysics, University of Delhi, Delhi - 110007, India

<sup>†</sup> CIMAP, CEA-CNRS-ENSICAEN-UNICAEN, Normandie Université, BP5133, F-14050 Caen Cedex 04, France

<sup>‡</sup> Normandie Université, ENSICAEN, UNICAEN, CNRS/IN2P3, LPC Caen, 14000 Caen, France

<sup>§</sup> Lawrence Berkley National Laboratory, Berkeley, CA-94720, USA

<sup>¶</sup> Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi - 110067, India

**Synopsis** The angular distribution of fragment emission with respect to the incoming beam direction is measured. In case of two body breakup of di-cationic molecular ions, such as $D_2O^{2+}$ and $C_2H_2^{2+}$, a strong anisotropy is observed when one of the fragments is an $H^+$ or $D^+$. These molecular ions were produced by impact of slow highly charged ions on neutral species. The technique of recoil ion momentum spectroscopy was used to measure the complete momentum vectors of all fragments in coincidence.

From the studies on fragmentation of charged molecular ions, it is becoming increasingly apparent that the emission of dissociation fragments is anisotropic in nature. In case of laser induced fragmentation, anisotropy had been observed with reference to the laser polarization axis [1] while for fragmentation induced by charged particles, the anisotropy is with respect to the incoming projectile beam [2]. Many of the studies reported in literature have focussed on diatomic molecules and results for polyatomic molecules are rather scarce.

We carried out experiments to address the anisotropic emission of fragment ions in two-body dissociation of few hydrogen (or deuteron) containing polyatomic molecules, such as $D_2O^{2+}$ and $C_2H_2^{2+}$, induced by impact of highly charged ions. The molecules considered for this study have very different geometries. The experiments were carried out at the Low Energy Ion Beam Facility (LEIBF) of Inter-University Accelerator Centre, Delhi, India and also at the ARIBE-GANIL facility in Caen, France. At both these facilities an electron cyclotron resonance (ECR) ion source was used to extract beams of highly charged ions. At LEIBF a recoil ion momentum spectrometer was used to measure the momenta of all ions in coincidence with the target gas being supplied by an effusive gas jet. At ARIBE-GANIL a COLTRIMS setup was used where the cold target molecules were produced using supersonic expansion. The facility at GANIL was also equipped with a post collision charge state analyzer which enabled us to separate events coming from pure ionization from the ones involving capture of one or two electrons.

The results of our experiments show strong anisotropic effects in the emission of recoil ion fragments with respect to the incoming projectile beam direction. These effects are common to all the

molecules considered during this investigation. As an example, the angular distribution of fragments $H^+$ and $C_2H^+$ produced from dissociation of $C_2H_2^{2+}$ is shown in the figure below.

<figure><img src="image_4.png" /><figcaption>**Figure 1.** Fragment angular distribution for two body breakup of $C_2H_2^{2+}$. Angle $\theta$ represents the angle between the fragment momentum vector and direction of the incoming projectile beam.</figcaption></figure>

The authors thank Indo-French Centre for Promotion of Advanced Research (IFCPAR/CEFIPRA) for supporting this collaboration (4604-2). JR thanks Department of Science and Technology, Government of India (SR/FTP/PS-098/2011) for financial support.

## References

[1] D. Pavičić et al. 2007 Phys. Rev. Lett. 98 243001

[2] J. Rajput and C. P. Safvan 2014 J. Chem. Phys. 141 164313

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<footnote n="1">¹E-mail: jrajput.du@gmail.com</footnote>

<footnote n="2">²E-mail: cp.safvan@gmail.com</footnote>