Four-dimensional dipole moment surfaces and local mode vibrational band intensities of GeH4

The local mode vibrational band intensities of GeH4 were calculated employing four-dimensional dipole moment surfaces (DMS) and local mode potential energy surfaces. Two kinds of DMS were tested: purely ab initio DMS from coupled cluster CCSD(T) calculations and effective DMS where selected higher-order terms in the former were optimized by fitting experimental intensities. Both DMS reproduce the intensities for transitions below 6500 cm−1 well. The effective DMS leads to better agreement for higher excitations and reproduces the intensity anomaly in the fourth local mode manifold.