The Paschen series consists of discrete spectral lines produced when electrons in a hydrogen atom transition from higher energy levels (n > 3) to the third energy level (n=3). These transitions emit photons with wavelengths located in the infrared region of the electromagnetic spectrum.

Electronic transitions involve electrons moving between energy levels within the electron cloud of an atom, resulting in the emission of photons in the infrared, visible, or ultraviolet ranges. Conversely, gamma (γ) rays are produced by transitions within the atomic nucleus itself, such as during radioactive decay or nuclear reactions. Therefore, gamma rays are not a product of electronic transitions.

Robert Bunsen and Gustav Kirchhoff pioneered spectral analysis in the mid-19th century. By comparing the emission spectra of chemical elements with the absorption lines in the solar spectrum (Fraunhofer lines), they successfully identified the chemical composition of the Sun's atmosphere.

The spectral series of hydrogen are defined by the final energy level (n_final) of the electron transition. The Lyman series ends at n=1, Balmer at n=2, Paschen at n=3, and the Brackett series ends at n=4. Therefore, when an electron transitions from a higher energy level to the 4th orbit, it emits a photon corresponding to a line in the Brackett series.

The spontaneous emission of a photon from an excited atom is a rapid process. Experimental measurements and quantum mechanical calculations indicate that the typical lifetime of an excited electronic state in an atom is on the order of 10^-8 seconds. This short duration reflects the high probability of the electron transitioning back to a lower energy state by emitting a photon.

The Lyman series corresponds to electron transitions ending at the n=1 energy level. Because the energy gap between n=1 and any higher level is significant, the emitted photons have high energy and short wavelengths, placing them in the ultraviolet range. In contrast, the Balmer series falls in the visible range, while the Paschen, Brackett, and Pfund series fall in the infrared range.

Electronic transitions involve electrons moving between energy levels within the electron cloud of an atom, which typically results in the emission of infrared, visible, or ultraviolet photons. Gamma rays, however, are produced by transitions within the atomic nucleus itself, involving changes in nuclear energy states, and therefore cannot be produced by electronic transitions.

A hydrogen discharge tube contains low-pressure gas excited by an electric current. As excited electrons return to lower energy states, they emit photons at specific, quantized frequencies. This results in a series of distinct, sharp lines known as a line spectrum. Unlike solids or dense gases that produce continuous spectra, atomic gases produce discrete lines corresponding to the energy transitions of their electrons.

The Paschen series corresponds to electronic transitions in a hydrogen atom where the electron falls to the third energy level (n=3) from higher levels (n > 3). These transitions emit photons with wavelengths that fall within the infrared region of the electromagnetic spectrum. Unlike continuous spectra, these appear as discrete lines representing specific energy differences between quantized atomic states.

The Lyman series corresponds to electronic transitions in a hydrogen atom ending at the ground state (n=1). Because the energy differences between the ground state and higher energy levels are large, the emitted photons have high energy, placing them in the ultraviolet region of the spectrum.