Mixed-State Ionic Beams: An Effective Tool for Collision Dynamics Investigations

• Main Authors: Emmanouil P. Benis, Ioannis Madesis, Angelos Laoutaris, Stefanos Nanos, Theo J. M. Zouros
• Format: Article
• Language: English
• Published: MDPI AG 2018-11-01
• Series: Atoms
• Subjects: zero-degree Auger projectile spectroscopy; mixed-state beams; metastable states; He-like states; Li-like states; Be-like states; cascade feeding; electron transfer excitation; electron excitation; electron transfer; hollow states; SIMION
• Online Access: https://www.mdpi.com/2218-2004/6/4/66

The use of mixed-state ionic beams in collision dynamics investigations is examined. Using high resolution Auger projectile spectroscopy involving He-like (<inline-formula> <math display="inline"> <semantics> <mrow> <mn>1</mn> <msup> <mi>s</mi> <mn>2</mn> </msup> <msup> <mspace width="0.166667em"></mspace> <mn>1</mn> </msup> <mspace width="-0.166667em"></mspace> <mi>S</mi> <mo>,</mo> <mn>1</mn> <mi>s</mi> <mn>2</mn> <mi>s</mi> <msup> <mspace width="0.166667em"></mspace> <mrow> <mn>3</mn> <mo>,</mo> <mn>1</mn> </mrow> </msup> <mspace width="-0.166667em"></mspace> <mi>S</mi> </mrow> </semantics> </math> </inline-formula>) mixed-state beams, the spectrum contributions of the <inline-formula> <math display="inline"> <semantics> <mrow> <mn>1</mn> <mi>s</mi> <mn>2</mn> <mi>s</mi> <msup> <mspace width="0.166667em"></mspace> <mn>3</mn> </msup> <mspace width="-0.166667em"></mspace> <mi>S</mi> </mrow> </semantics> </math> </inline-formula> metastable beam component is effectively separated and clearly identified. This is performed with a technique that exploits two independent spectrum measurements under the same collision conditions, but with ions having quite different metastable fractions, judiciously selected by varying the ion beam charge-stripping conditions. Details of the technique are presented together with characteristic examples. In collisions of 4 MeV B<inline-formula> <math display="inline"> <semantics> <msup> <mrow></mrow> <mrow> <mn>3</mn> <mo>+</mo> </mrow> </msup> </semantics> </math> </inline-formula> with H<inline-formula> <math display="inline"> <semantics> <msub> <mrow></mrow> <mn>2</mn> </msub> </semantics> </math> </inline-formula> targets, the Auger electron spectrum of the separated <inline-formula> <math display="inline"> <semantics> <mrow> <mn>1</mn> <mi>s</mi> <mn>2</mn> <mi>s</mi> <msup> <mspace width="0.166667em"></mspace> <mn>3</mn> </msup> <mi>S</mi> <mspace width="-0.166667em"></mspace> </mrow> </semantics> </math> </inline-formula> boron beam component allows for a detailed analysis of the formation of the <inline-formula> <math display="inline"> <semantics> <mrow> <mn>1</mn> <mi>s</mi> <mn>2</mn> <mi>s</mi> <mrow> <msup> <mo>(</mo> <mn>3</mn> </msup> <mspace width="-0.166667em"></mspace> <mi>S</mi> <mo>)</mo> </mrow> <mi>n</mi> <mi>l</mi> <msup> <mspace width="0.166667em"></mspace> <mn>2</mn> </msup> <mspace width="-0.166667em"></mspace> <mi>L</mi> </mrow> </semantics> </math> </inline-formula> states by direct <inline-formula> <math display="inline"> <semantics> <mrow> <mi>n</mi> <mi>l</mi> </mrow> </semantics> </math> </inline-formula> transfer. In addition, the production of hollow <inline-formula> <math display="inline"> <semantics> <mrow> <mn>2</mn> <mi>s</mi> <mn>2</mn> <mi>p</mi> <msup> <mspace width="0.166667em"></mspace> <mrow> <mn>1</mn> <mo>,</mo> <mn>3</mn> </mrow> </msup> <mspace width="-0.166667em"></mspace> <mi>P</mi> </mrow> </semantics> </math> </inline-formula> doubly- and <inline-formula> <math display="inline"> <semantics> <mrow> <mn>2</mn> <mi>s</mi> <mn>2</mn> <msup> <mi>p</mi> <mn>2</mn> </msup> <msup> <mspace width="0.166667em"></mspace> <mn>2</mn> </msup> <mspace width="-0.166667em"></mspace> <mi>D</mi> </mrow> </semantics> </math> </inline-formula> triply-excited states, by direct excitation and transfer-excitation processes, respectively, can also be independently studied. In similar mixed-state beam collisions of 15 MeV C<inline-formula> <math display="inline"> <semantics> <msup> <mrow></mrow> <mrow> <mn>4</mn> <mo>+</mo> </mrow> </msup> </semantics> </math> </inline-formula> with H<inline-formula> <math display="inline"> <semantics> <msub> <mrow></mrow> <mn>2</mn> </msub> </semantics> </math> </inline-formula>, He, Ne and Ar targets, the contributions of the <inline-formula> <math display="inline"> <semantics> <mrow> <mn>1</mn> <msup> <mi>s</mi> <mn>2</mn> </msup> </mrow> </semantics> </math> </inline-formula>, <inline-formula> <math display="inline"> <semantics> <mrow> <mn>1</mn> <mi>s</mi> <mn>2</mn> <mi>s</mi> <msup> <mspace width="0.166667em"></mspace> <mrow> <mn>3</mn> <mo>,</mo> <mn>1</mn> </mrow> </msup> <mi>S</mi> </mrow> </semantics> </math> </inline-formula> beam components to the formation of the <inline-formula> <math display="inline"> <semantics> <mrow> <mn>2</mn> <mi>s</mi> <mn>2</mn> <mi>p</mi> <msup> <mspace width="0.166667em"></mspace> <mrow> <mn>3</mn> <mo>,</mo> <mn>1</mn> </mrow> </msup> <mspace width="-0.166667em"></mspace> <mi>P</mi> </mrow> </semantics> </math> </inline-formula> states by double-excitation, <inline-formula> <math display="inline"> <semantics> <mrow> <mn>1</mn> <mi>s</mi> <mo>&#8594;</mo> <mn>2</mn> <mi>p</mi> </mrow> </semantics> </math> </inline-formula> excitation and transfer-loss processes can be clearly identified, facilitating comparisons with theoretical calculations.