Single-conformation spectroscopy has been used to study two cyclically constrained and capped gamma-peptides: Ac-gamma(ACHC)-NHBn (hereafter gamma(ACHC), Figure 1a), and Ac-gamma(ACHC)-gamma(ACHC)-NHBn (gamma gamma(ACHC), Figure 1b), under jet-cooled conditions in the gas phase. The gamma-peptide backbone in both molecules contains a cyclohexane ring incorporated across each C beta-C gamma bond and an ethyl group at each C alpha. This substitution pattern was designed to stabilize a (g+, g+) torsion angle sequence across the C alpha-C beta-C gamma segment of each gamma-amino acid residue. Resonant two-photon ionization (R2PI), infrared-ultraviolet hole-burning (IR-UV HB), and resonant ion-dip infrared (RIDIR) spectroscopy have been used to probe the single-conformation spectroscopy of these molecules. In both gamma(ACHC) and gamma gamma(ACHC), all population is funneled into a single conformation. With RIDIR spectra in the NH stretch (3200-3500 cm(-1)) and amide I/II regions (1400-1800 cm(-1)), in conjunction with theoretical predictions, assignments have been made for the conformations observed in the molecular beam. gamma(ACHC) forms a single nearest-neighbor C9 hydrogen-bonded ring whereas gamma gamma(ACHC) takes up a next-nearest-neighbor C14 hydrogen-bonded structure. The gas-phase C14 conformation represents the beginning of a 2.6(14)-helix, suggesting that the constraints imposed on the gamma-peptide backbone by the ACHC and ethyl groups already impose this preference in the gas-phase di-gamma-peptide, in which only a single C14 H-bond is possible, constituting one full turn of the helix. A similar conformational preference was previously documented in crystal structures and NMR analysis of longer gamma-peptide oligomers containing the gamma(ACHC) subunit [Guo, L., et al. Angew. Chem. Int. Ed. 2011, 50, 5843-5846]. In the gas phase, the gamma(ACHC)-H2O complex was also observed and spectroscopically interrogated in the molecular beam. Here, the monosolvated gamma(ACHC) retains the C9 hydrogen bond observed in the bare molecule, with the water acting as a bridge between the C-terminal carbonyl and the pi-cloud of the UV chromophore. This is in contrast to the unconstrained gamma-peptide-H2O complex, which incorporates H2O into both C9 and amide-stacked conformations.