New experimental possibilities and the future at far IR wavelengths

The observation of molecular phenomena in interstellar clouds through spectroscopy in the longer wavelength region of the infrared is discussed. This is a region where sensitivity is almost universally influenced by background continua; appropriate methods may be either coherent or incoherent, and work above most of the atmosphere is required for much of the spectral range. Thus far, only a very limited amount of molecular work has been done in the far-infrared, but rapid growth and important results are to be expected.