On Resonance Enhancement of <i>E</i>1-<i>E</i>2 Nondipole Photoelectron Asymmetries in Low-Energy Ne 2<i>p</i> Photoionization
Earlier, a significant enhancement of the nondipole parameters <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>γ</mi><mrow><mn>2</mn><mi>p</mi></mrow><...
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| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2024-11-01
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| Series: | Atoms |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2218-2004/12/11/58 |
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| Summary: | Earlier, a significant enhancement of the nondipole parameters <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>γ</mi><mrow><mn>2</mn><mi>p</mi></mrow></msub></semantics></math></inline-formula>, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>δ</mi><mrow><mn>2</mn><mi>p</mi></mrow></msub></semantics></math></inline-formula>, and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>ζ</mi><mrow><mn>2</mn><mi>p</mi></mrow></msub><mo>=</mo><msub><mi>γ</mi><mrow><mn>2</mn><mi>p</mi></mrow></msub><mo>+</mo><mn>3</mn><msub><mi>δ</mi><mrow><mn>2</mn><mi>p</mi></mrow></msub></mrow></semantics></math></inline-formula> in the photoelectron angular distribution for Ne <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>2</mn><mi>p</mi></mrow></semantics></math></inline-formula> photoionization was predicted, owing to resonance interference between dipole (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>E</mi><mn>1</mn></mrow></semantics></math></inline-formula>) and quadrupole (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>E</mi><mn>2</mn></mrow></semantics></math></inline-formula>) transitions. This enhancement manifests as narrow resonance spikes in the parameters due to the low-energy <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>2</mn><mi>s</mi><mo>→</mo><mn>3</mn><mi>p</mi></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>2</mn><mi>s</mi><mo>→</mo><mn>4</mn><mi>p</mi></mrow></semantics></math></inline-formula> dipole, as well as the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>2</mn><mi>s</mi><mo>→</mo><mn>3</mn><mi>d</mi></mrow></semantics></math></inline-formula> quadrupole autoionizing resonances. Given the unique nature of this predicted enhancement, it requires further validation, specifically regarding whether these narrow spikes in <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>γ</mi><mrow><mn>2</mn><mi>p</mi></mrow></msub></semantics></math></inline-formula>, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>δ</mi><mrow><mn>2</mn><mi>p</mi></mrow></msub></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>ζ</mi><mrow><mn>2</mn><mi>p</mi></mrow></msub></semantics></math></inline-formula> will or will not retain their values for experimental observation if one accounts for a typical finite frequency spread in the ionizing radiation. To address this, we revisit the previous study, now incorporating the effect of frequency spread in the ionizing radiation, assuming a spread as large as 5 meV at the half-maximum of the radiation’s intensity. In the present paper we demonstrate that while the frequency spread does affect the resonance enhancement of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>γ</mi><mrow><mn>2</mn><mi>p</mi></mrow></msub></semantics></math></inline-formula>, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>δ</mi><mrow><mn>2</mn><mi>p</mi></mrow></msub></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>ζ</mi><mrow><mn>2</mn><mi>p</mi></mrow></msub></semantics></math></inline-formula>, these parameters still retain quantitatively significant values to be observed experimentally. The corresponding calculations were performed using the random phase approximation with exchange, which accounts for interchannel coupling in both dipole and quadrupole photoionization amplitudes. |
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| ISSN: | 2218-2004 |