Question

1. Order the following processes by increasing wavelength: excitation, fluorescence, phosphorescence.Explain your answer in terms of the energy gap between the ground and excited states.

2. Compare and contrast the three atom sources for AA and AE measurements in terms of sensitivity and interferences.

3. Light can excite vibrational, rotational, or electronic modes in molecules. Which type of light (IR, UV/VIS, microwave) causes which excitation mode?

Answer 1

Increasing wavelength excitation < fluorescence <phosphoresance

At first molecule is excited to any higher electronic energy level. These excited states are accompanied by lots of vibrational states, excitation occurs from any of them. But fluorescence always occur from lowest vibrational levels of excited electronic state. So, energy is obviously lower. For phosphorescence , energy is released from an intermediate level. So, order is as follows.