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PRACTICE / Characteristic and continuous X-ray spectra

The missing line has a threshold

A simplified target model has K and L levels at −11.2 keV and −2.8 keV. Inner shells are initially filled. A tube operating at 9.0 kV is to be raised just to the ideal threshold for direct electron-impact creation of K vacancies.

What increase in accelerating voltage reaches that threshold?

Organize the givens & assumptions
  • EK = −11.2 keV
  • EL = −2.8 keV
  • Initial tube voltage = 9.0 kV

Elementary ionization model with a zero-energy free-electron reference; negligible incident initial kinetic energy; an energy threshold alone does not guarantee measurable emission.

  1. A0 kV0\ \mathrm{kV}
  2. B8.4 kV8.4\ \mathrm{kV}
  3. C11.2 kV11.2\ \mathrm{kV}
  4. D2.2 kV2.2\ \mathrm{kV}

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