Which of the following processes causes the emission of X-ray?

Options

A. `alpha`-emission
B. `beta`-emission
C. `beta^(+)` (Positron) emission
D. electron capture

Answer

To determine which process causes the emission of X-rays, we need to analyze the provided options: alpha emission, beta emission, beta plus (positron) emission, and electron capture.

### Step-by-Step Solution:

1. **Understanding X-ray Emission**:
- X-rays are high-energy electromagnetic radiation. They are typically produced when electrons transition between energy levels in an atom or when high-energy electrons collide with matter.

2. **Analyzing the Processes**:
- **Alpha Emission**: This involves the release of alpha particles (helium nuclei) from a nucleus. This process does not involve electron transitions and does not produce X-rays.
- **Beta Emission**: This involves the transformation of a neutron into a proton (or vice versa) with the emission of beta particles (electrons or positrons). While it involves electrons, it does not directly lead to X-ray emission.
- **Beta Plus (Positron) Emission**: This is the emission of a positron from a nucleus. Similar to beta emission, it does not result in X-ray production.
- **Electron Capture**: In this process, an electron from an inner shell is captured by the nucleus, which can lead to a vacancy in that shell. When an electron from a higher energy level falls into this vacancy, it releases energy in the form of X-rays.

3. **Conclusion**:
- The process that causes the emission of X-rays is **Electron Capture**. When an electron is captured by the nucleus, it leads to the emission of X-rays as other electrons transition to fill the vacancy.

### Final Answer:
**Electron Capture** is the process that causes the emission of X-rays.

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