Chapter 11: Problem 7
Estimate the ratio of the term in (39.9) that is linear in \(\mathrm{H}\) to the kinetic-energy term, for a hydrogen atom in a magnetic field of \(10^{5}\) gauss.
Short Answer
Expert verified
The ratio of the term linear in H to the kinetic-energy term is approximately \( \frac{e H L_z}{p^2 c} \).
Step by step solution
01
- Identify the linear term in \(\text{H}\)
The term linear in \(\text{H}\) for a hydrogen atom in a magnetic field is the Zeeman effect term, given by \( \frac{e \text{H}}{2m_e c} L_z \), where \( e \) is the electron charge, \( m_e \) is the electron mass, \( c \) is the speed of light, and \( L_z \) is the z-component of the angular momentum.
02
- Write down the expression for the kinetic energy term
The kinetic energy of the electron in a hydrogen atom is given by \( T = \frac{p^2}{2m_e} \), where \( p \) is the momentum of the electron.
03
- Estimate the ratio
To find the ratio of the linear term \( \frac{e H}{2m_e c} L_z \) to the kinetic energy term \( \frac{p^2}{2m_e} \), evaluate \(\frac{e H L_z}{p^2 c} \). Using the given magnetic field \( H = 10^5 \) gauss (which is \( 10^{-1} \) tesla) and estimating \( p \) based on the principal quantum number, the ratio is approximately \(\frac{e H L_z}{p^2 c} \). For \( L_z \) we can use \( \frac{h}{2\text{π}} m \) and for \( p^2 \) it can be approximated by \( m_e^2 e^4 / ℏ^2 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Zeeman Effect
The Zeeman effect is an important phenomenon in atomic physics that occurs when an atom is exposed to a magnetic field. This magnetic field causes the energy levels of the atom's electrons to split into multiple closely spaced levels. These new energy levels depend on the magnetic field's strength and the specific characteristics of the electrons, such as their magnetic moment. This splitting is known as the Zeeman effect.
In the case of the hydrogen atom, the term linear in the magnetic field (\text{H}) represents the interaction between the magnetic field and the electron's magnetic moment. The mathematical representation of this interaction can be given by: \(\frac{e \text{H}}{2m_e c} L_z\). Here,
In the case of the hydrogen atom, the term linear in the magnetic field (\text{H}) represents the interaction between the magnetic field and the electron's magnetic moment. The mathematical representation of this interaction can be given by: \(\frac{e \text{H}}{2m_e c} L_z\). Here,
- \text{e} is the electron charge.
- \text{H} is the magnetic field strength.
- \text{m}\text{e} is the electron mass.
- \text{c} is the speed of light.
- \text{L}\text{z} represents the z-component of the electron's angular momentum.
Kinetic Energy
Kinetic energy is the energy possessed by an object due to its motion. In the context of an electron in a hydrogen atom, kinetic energy represents the energy due to the electron's movement around the nucleus. The expression for the kinetic energy of an electron in a hydrogen atom is given by: \(\text{T} = \frac{p^2}{2m_e}\). Here,
- \text{T} is the kinetic energy.
- \text{p} is the momentum of the electron.
- \text{m}\text{e} stands for the mass of the electron.
Magnetic Field
A magnetic field (\text{H}) is a field produced by moving electric charges or magnetic dipoles and affects the behavior of charged particles within its vicinity. In the exercise, the magnetic field strength is given as 105 gauss, which is equivalent to 0.1 tesla. This magnetic field impacts the hydrogen atom, causing the split in the energy levels of the electrons, which is observed as the Zeeman effect.
The strength and orientation of the magnetic field determine the degree of splitting and the energy shifts within the atom. The expression linking the magnetic field to the Zeeman effect term is: \(\frac{e \text{H}}{2m_e c} L_z\) . Here,
The strength and orientation of the magnetic field determine the degree of splitting and the energy shifts within the atom. The expression linking the magnetic field to the Zeeman effect term is: \(\frac{e \text{H}}{2m_e c} L_z\) . Here,
- \text{H} is the magnetic field strength.
- \text{e} is the electron charge.
- \text{m}\text{e} is the electron mass.
- \text{c} is the speed of light.
- \text{L}\text{z} is the z-component of the angular momentum.
Electron Momentum
Momentum (\text{p}) is a fundamental physical quantity representing the product of an object's mass and velocity. For an electron in a hydrogen atom, the momentum plays a key role in describing its motion around the nucleus. The relationship between momentum and kinetic energy is given by the formula: \(\text{T} = \frac{p^2}{2m_e}\) . Here,
- \text{T} is the kinetic energy.
- \text{p} represents the momentum.
- \text{m}\text{e} is the mass of the electron.
Angular Momentum
Angular momentum (\text{L}) is a measure of the amount of rotation an object has, taking into account its mass distribution and rotational velocity. For electrons in atoms, angular momentum is quantized, meaning it can only take on discrete values. The z-component of the electron's angular momentum (\text{L}\text{z}) plays a vital role in the Zeeman effect.
In the context of the given problem, the z-component of angular momentum, \text{L}\text{z}, is given by the relation: \(\text{L}_z = \frac{h}{2\text{π}} m\) . Here,
In the context of the given problem, the z-component of angular momentum, \text{L}\text{z}, is given by the relation: \(\text{L}_z = \frac{h}{2\text{π}} m\) . Here,
- \text{h} is Planck's constant.
- \text{π} is pi, a mathematical constant.
- \text{m} represents the magnetic quantum number.